Light detection and ranging (LIDAR) device range aliasing resilience by multiple hypotheses

ABSTRACT

A computing system may operate a LIDAR device to emit light pulses in accordance with a time sequence including a time-varying dither. The system may then determine that the LIDAR detected return light pulses during corresponding detection periods for each of two or more emitted light pulses. Responsively, the system may determine that the detected return light pulses have (i) detection times relative to corresponding emission times of a plurality of first emitted light pulses that are indicative of a first set of ranges and (ii) detection times relative to corresponding emission times of a plurality of second emitted light pulses that are indicative of a second set of ranges. Given this, the system may select between using the first set of ranges as a basis for object detection and using the second set of ranges as a basis for object detection, and may then engage in object detection accordingly.

BACKGROUND

A vehicle can be configured to operate in an autonomous mode in whichthe vehicle navigates through an environment with little or no inputfrom a driver. Such an autonomous vehicle can include one or moresensors that are configured to detect information about the environmentin which the vehicle operates. One such sensor is a light detection andranging (LIDAR) device.

A LIDAR device can estimate distance to environmental features whilescanning through a scene to assemble a “point cloud” indicative ofreflective surfaces in the environment. Individual points in the pointcloud can be determined by transmitting a laser pulse and detecting areturning pulse, if any, reflected from an object in the environment,and determining the distance to the object according to the time delaybetween the transmitted pulse and the reception of the reflected pulse.

A LIDAR device may thus include a laser, or set of lasers, and mayrapidly and repeatedly scan across a scene to provide continuousreal-time information on distances to reflective objects in the scene.Combining the measured distances and the orientation of the laser(s)while measuring each distance allows for associating a three-dimensionalposition with each returning pulse. In this way, a three-dimensional mapof points indicative of locations of reflective features in theenvironment can be generated for the entire scanning zone.

One challenge in using LIDARs can be range aliasing. Range aliasingrelates to the appearance of ambiguous echoes, such as when a systemcannot disambiguate between a signal scattered from one particular rangeand a signal scattered from other ranges based on the generated data.For example, in the context of LIDARs, range aliasing can refer a returnsignal from outside a LIDAR's maximum unambiguous range beinginterpreted to be within the LIDAR's maximum unambiguous range.

SUMMARY

This disclosure relates generally to sensors, and in particular tosystems and methods that provide range aliasing resilience for sensors.

Example implementations may relate to generating multiple rangehypotheses during operation of a LIDAR device. Once generated, themultiple range hypotheses could be used by a computing system, e.g.,onboard or remote, to disambiguate multiple return signals receivedduring a listening/detection period, associate with each or a subset ofthe return signals a range that has a greater likelihood of representinga physical state of the environment, and/or to detect an objectpositioned outside of a nominal unambiguous detection range of the LIDARdevice. For example, an alternate range hypothesis (e.g., a rangehypothesis other than a default range hypothesis) could be used by thecomputing system to detect an object positioned outside a maximumunambiguous detection range of the LIDAR device.

As a further example, consider a scenario in which a LIDAR device emitsa first pulse, listens for return signals during a first detectionperiod, emits a second pulse, and listens for return signals during asecond detection period. Under one hypothesis, any return signalsdetected during a detection period is associated with the pulse emittedimmediately preceding the detection period. For example, any returnsignals detected during the first detection period is associated withthe first pulse, and any return signals detected during the seconddetection period is associated with the second pulse. Accordingly, underthis hypothesis, which may be referred to herein as the default rangehypothesis, a detected return signal is associated with the mostrecently emitted pulse, and the difference between the time the mostrecently emitted pulse was emitted and the time the return signal wasdetected is used to compute the distance the pulse traveled. Thisdistance is associated with a range and bearing of the object thatreflected the pulse.

Under an alternate hypothesis, the detected return signal is not fromthe most recently emitted pulse. For example, a subset of return signalsdetected during the second detection period may be associated with thefirst pulse rather than the second pulse, and the distance the pulsetraveled is calculated based on the difference between the time thefirst pulse was emitted and the time the return signal was detected.

As a further example, consider a scenario in which, during a detectionperiod (e.g., the second detection period), a LIDAR device detectsreturn light pulses that actually correspond to more than one emittedlight pulses (e.g., the first pulse and the second pulse). This cancreate ambiguity as to whether a given return light pulse corresponds tothe pulse emission occurring immediately before the detection period(e.g., the second pulse), or whether the given return light pulsecorresponds to a pulse emission that occurred earlier in time, e.g.,before a previous detection period (e.g., the first pulse). Thisambiguity can arise, for example, when a return light pulse is detectedafter being reflected off an object positioned outside a nominaldetection range of a LIDAR device.

In accordance with the disclosed implementations, the computing systemcould operate the LIDAR device to emit light pulses in accordance with atime sequence that includes a time-varying dither and, once return lightpulses are detected, could generate two or more range hypotheses.

For instance, after the LIDAR device detects return light pulses, thecomputing system may determine (i) a first set of ranges in accordancewith a time delay relative to corresponding emission times of aplurality of first emitted light pulses and (ii) a second set of rangesin accordance with a time delay relative to corresponding emission timesof a plurality of second emitted light pulses.

In some examples, the first set of ranges could correspond to a “closerange hypothesis” and the second set of ranges could correspond to a“far range hypothesis.” In the “close range hypothesis,” for eachdetected light pulse, a respective range is determined in accordancewith a time delay relative to an emission time of a light pulseassociated with the detection period during which the light pulse wasdetected. For example, in the scenario above, the close range hypothesismay correspond to the default range hypothesis. In the “far rangehypothesis,” for each detected light pulse, a respective range isdetermined in accordance with a time delay relative to an emission timeof a light pulse associated with a preceding detection period (e.g., adetection period that precedes in time the detection period during whichthe light pulse was detected). For example, in the scenario above, thefar range hypothesis may correspond to the alternate range hypothesis.However, as further discussed herein, it should be understood that otherrange hypotheses are possible as well.

Based on one or more factors, the computing system could then selectbetween using the first set of ranges as a basis for object detectionand using the second set of ranges as a basis for object detection. Byway of example, the computing system may select the set having rangesthat more closely resemble a known object rather than selecting the sethaving ranges that do not resemble a known object and/or may select theset that includes ranges that are substantially similar to one anotherrather than selecting the set that includes ranges that aresubstantially different from one another, among other options.

Furthermore, as noted, the present disclosure could apply in the contextof disambiguating between multiple light pulses detected during the samedetection period and/or in the context of detecting an object positionedoutside the nominal detection range of the LIDAR device. In particular,a LIDAR device could sometimes detect multiple light pulses respectivelyduring each of a plurality of detection periods, and the computingsystem could determine how these return light pulses should be used asbasis for object detection.

For instance, each detection period may include detection of a firstreturn light pulse that corresponds to the emitted light pulseassociated with that detection period (e.g., the light pulse emittedimmediately prior to that detection period) and may also includedetection of a second return light pulse that reflected off an objectpositioned outside of the nominal unambiguous detection range and thuscorresponds to an emitted light pulse associated with another detectionperiod (e.g., the light pulse emitted prior to a preceding detectionperiod).

In accordance with the disclosed implementations, in order to determinehow such return light pulses should be used as basis for objectdetection, a system could emit light pulses in accordance with a timesequence that includes a time-varying dither, and generate and utilizemultiple range hypotheses. For example, the system may determine a firstset of ranges according to a close range hypothesis for the first returnlight pulses as well as a second set of ranges according to a closerange hypothesis for the second return light pulses. Additionally, thesystem may determine a third set of ranges according to an alternaterange hypothesis (e.g., a far range hypothesis) for the second returnlight pulses. With this information, the computing system could thendetect an object positioned outside the nominal unambiguous detectionrange of a LIDAR device and/or could disambiguate between multiplereturn light pulses detected during the same detection period(s).

For instance, the computing system could determine whether or not theset of third ranges assembles a point cloud indicative of at least oneknown object. If so, then the computing system could use that set ofthird ranges as basis for object detection. This, in turn, can enabledetection of objects positioned outside the nominal unambiguousdetection range of the LIDAR device.

Moreover, if the set of third ranges assembles a point cloud indicativeof at least one known object, then the computing system could determinethat the alternate range hypothesis for the second return light pulsesis likely correct. Namely, that the second return light pulses likelyeach respectively correspond to an alternate preceding pulse emissionrather than to a nominal pulse emission. And based on the determinationthat the alternate range hypothesis for the second return light pulsesis likely correct, the computing system may determine that the closerange hypothesis for the second return light pulses is likely incorrect.Thus, the computing system could responsively determine that thecomputing system should use, for purposes of object detection, the firstset of ranges associated with the first return light pulses rather thanthe second set of ranges associated with the second return light pulses,thereby resolving range ambiguity. Other examples are also possible.

In one aspect, a method is disclosed. The method involves operating, bya computing system, a Light Detection and Ranging (LIDAR) device to emitlight pulses at emission times in accordance with an emission timesequence, where the emission time sequence includes a time-varyingdither, and to detect return light pulses in accordance with a detectiontime sequence, where the detection time sequence includes, for eachemitted light pulse, a corresponding detection period for detection of acorresponding return light pulse, and where a detection time of a returnlight pulse relative to a corresponding emission time of a correspondingemitted light pulse is indicative of a range to an object that reflectedthe corresponding emitted light pulse. The method also involves making adetermination, by the computing system, that the LIDAR device detectedreturn light pulses during corresponding detection periods for each oftwo or more emitted light pulses. The method additionally involves, inresponse to making the determination, determining, by the computingsystem, that (i) the detected return light pulses have detection timesrelative to corresponding emission times of a plurality of first emittedlight pulses that are indicative of a first set of ranges and (ii) thedetected return light pulses have detection times relative tocorresponding emission times of a plurality of second emitted lightpulses that are indicative of a second set of ranges. The method furtherinvolves selecting, by the computing system, between using the first setof ranges as a basis for object detection and using the second set ofranges as a basis for object detection. The method yet further involvesengaging, by the computing system, in object detection in accordancewith the selecting.

In another aspect, a computing system is disclosed. The computing systemincludes one or more processors, a non-transitory computer readablemedium, and program instructions stored on the non-transitory computerreadable medium and executable by the one or more processors. Inparticular, the program instructions may be executable to operate aLight Detection and Ranging (LIDAR) device to emit light pulses atemission times in accordance with an emission time sequence, where theemission time sequence includes a time-varying dither, and to detectreturn light pulses in accordance with a detection time sequence, wherethe detection time sequence includes, for each emitted light pulse, acorresponding detection period for detection of a corresponding returnlight pulse, and where a detection time of a return light pulse relativeto a corresponding emission time of a corresponding emitted light pulseis indicative of a range to an object that reflected the correspondingemitted light pulse. The program instructions may also be executable tomake a determination that the LIDAR device detected return light pulsesduring corresponding detection periods for each of two or more emittedlight pulses. The program instructions may additionally be executableto, in response to making the determination, determine that (i) thedetected return light pulses have detection times relative tocorresponding emission times of a plurality of first emitted lightpulses that are indicative of a first set of ranges and (ii) thedetected return light pulses have detection times relative tocorresponding emission times of a plurality of second emitted lightpulses that are indicative of a second set of ranges. The programinstructions may further be executable to select between using the firstset of ranges as a basis for object detection and using the second setof ranges as a basis for object detection. The program instructions mayyet further be executable to engage in object detection in accordancewith the selecting.

In yet another aspect, another method is disclosed. The method involvesoperating, by a computing system, a Light Detection and Ranging (LIDAR)device to emit light pulses at emission times in accordance with anemission time sequence, where the emission time sequence includes atime-varying dither, and to detect return light pulses in accordancewith a detection time sequence, where the detection time sequenceincludes, for each emitted light pulse, a corresponding detection periodfor detection of a corresponding return light pulse, and where adetection time of a return light pulse relative to a correspondingemission time of a corresponding emitted light pulse is indicative of arange to an object that reflected the corresponding emitted light pulse.The method also involves determining, by the computing system, that theLIDAR device detected a set of multiple return light pulses duringcorresponding detection periods for each of a plurality of first emittedlight pulses, where each set of multiple return light pulses includes atleast a respective first return light pulse and a respective secondreturn light pulse. The method additionally involves making adetermination, by the computing system, that the first return lightpulses correspond to the plurality of first emitted light pulses andthat the second return light pulses potentially correspond to aplurality of second emitted light pulses. The method further involves,in response to making the determination, determining, by the computingsystem, that the second return light pulses have detection timesrelative to corresponding emission times of the plurality of secondemitted light pulses that are indicative of a particular set of ranges.The method yet further involves making a further determination, by thecomputing system, of whether or not to use the particular set of rangesas a basis for object detection. The method yet further involvesengaging, by the computing system, in object detection in accordancewith the further determination.

In yet another aspect, another method is disclosed. The method involvesoperating, by a computing system, a Light Detection and Ranging (LIDAR)device to emit light pulses at emission times in accordance with anemission time sequence, where the emission time sequence includes atime-varying dither, and to detect return light pulses in accordancewith a detection time sequence, where the detection time sequenceincludes, for each emitted light pulse, a corresponding detection periodfor detection of a corresponding return light pulse, and where adetection time of a return light pulse relative to a correspondingemission time of a corresponding emitted light pulse is indicative of arange to an object that reflected the corresponding emitted light pulse.The method also involves determining, by the computing system, that theLIDAR device detected a set of multiple return light pulses duringcorresponding detection periods for each of a plurality of first emittedlight pulses, where each set of multiple return light pulses includes atleast a respective first return light pulse and a respective secondreturn light pulse. The method additionally involves determining, by thecomputing system, that (i) the first return light pulses have detectiontimes relative to corresponding emission times of the plurality of firstemitted light pulses that are indicative of a first set of ranges, (ii)the second return light pulses have detection times relative tocorresponding emission times of the plurality of first emitted lightpulses that are indicative of a second set of ranges, and (iii) thesecond return light pulses have detection times relative tocorresponding emission times of a plurality of second emitted lightpulses that are indicative of a third set of ranges. The method furtherinvolves, based on the third set of ranges, selecting, by the computingsystem, between using the first set of ranges as a basis for objectdetection and using the second set of ranges as a basis for objectdetection. The method yet further involves engaging, by the computingsystem, in object detection in accordance with the selecting.

In yet another aspect, a method for operating an autonomous vehicle isdisclosed. The method involves receiving a signal associated with areflection, by an object, of a light pulse emitted by a LIDAR device ofthe autonomous vehicle. The method also involves calculating a firstdistance to the object based on a first time, the first timecorresponding to a prior light pulse emitted by the LIDAR device of theautonomous vehicle. The method additionally involves calculating asecond distance to the object based on a second time, the second timecorresponding to a different prior light pulse emitted by the LIDARdevice of the autonomous vehicle. The method further involves operatingthe autonomous vehicle based on a selection between the first distanceand second distance.

In yet another aspect, another system is disclosed. The system mayinclude means for operating a Light Detection and Ranging (LIDAR) deviceto emit light pulses at emission times in accordance with an emissiontime sequence, where the emission time sequence includes a time-varyingdither, and to detect return light pulses in accordance with a detectiontime sequence, where the detection time sequence includes, for eachemitted light pulse, a corresponding detection period for detection of acorresponding return light pulse, and where a detection time of a returnlight pulse relative to a corresponding emission time of a correspondingemitted light pulse is indicative of a range to an object that reflectedthe corresponding emitted light pulse. The system may also include meansfor making a determination that the LIDAR device detected return lightpulses during corresponding detection periods for each of two or moreemitted light pulses. The system may additionally include means for, inresponse to making the determination, determining that (i) the detectedreturn light pulses have detection times relative to correspondingemission times of a plurality of first emitted light pulses that areindicative of a first set of ranges and (ii) the detected return lightpulses have detection times relative to corresponding emission times ofa plurality of second emitted light pulses that are indicative of asecond set of ranges. The system may further include means for selectingbetween using the first set of ranges as a basis for object detectionand using the second set of ranges as a basis for object detection. Thesystem may yet further include means for engaging in object detection inaccordance with the selecting.

In yet another aspect, another system is disclosed. The system mayinclude means for operating a Light Detection and Ranging (LIDAR) deviceto emit light pulses at emission times in accordance with an emissiontime sequence, where the emission time sequence includes a time-varyingdither, and to detect return light pulses in accordance with a detectiontime sequence, where the detection time sequence includes, for eachemitted light pulse, a corresponding detection period for detection of acorresponding return light pulse, and where a detection time of a returnlight pulse relative to a corresponding emission time of a correspondingemitted light pulse is indicative of a range to an object that reflectedthe corresponding emitted light pulse. The system may also include meansfor determining that the LIDAR device detected a set of multiple returnlight pulses during corresponding detection periods for each of aplurality of first emitted light pulses, where each set of multiplereturn light pulses includes at least a respective first return lightpulse and a respective second return light pulse. The system mayadditionally include means for making a determination that the firstreturn light pulses correspond to the plurality of first emitted lightpulses and that the second return light pulses potentially correspond toa plurality of second emitted light pulses. The system may furtherinclude means for, in response to making the determination, determiningthat the second return light pulses have detection times relative tocorresponding emission times of the plurality of second emitted lightpulses that are indicative of a particular set of ranges. The system mayyet further include means for making a further determination of whetheror not to use the particular set of ranges as a basis for objectdetection. The system may yet further include means for engaging inobject detection in accordance with the further determination.

In yet another aspect, another system is disclosed. The system mayinclude means for operating a Light Detection and Ranging (LIDAR) deviceto emit light pulses at emission times in accordance with an emissiontime sequence, where the emission time sequence includes a time-varyingdither, and to detect return light pulses in accordance with a detectiontime sequence, where the detection time sequence includes, for eachemitted light pulse, a corresponding detection period for detection of acorresponding return light pulse, and where a detection time of a returnlight pulse relative to a corresponding emission time of a correspondingemitted light pulse is indicative of a range to an object that reflectedthe corresponding emitted light pulse. The system may also include meansfor determining that the LIDAR device detected a set of multiple returnlight pulses during corresponding detection periods for each of aplurality of first emitted light pulses, where each set of multiplereturn light pulses includes at least a respective first return lightpulse and a respective second return light pulse. The system mayadditionally include means for determining that (i) the first returnlight pulses have detection times relative to corresponding emissiontimes of the plurality of first emitted light pulses that are indicativeof a first set of ranges, (ii) the second return light pulses havedetection times relative to corresponding emission times of theplurality of first emitted light pulses that are indicative of a secondset of ranges, and (iii) the second return light pulses have detectiontimes relative to corresponding emission times of a plurality of secondemitted light pulses that are indicative of a third set of ranges. Thesystem may further include means for, based on the third set of ranges,selecting between using the first set of ranges as a basis for objectdetection and using the second set of ranges as a basis for objectdetection. The system may yet further include means for engaging inobject detection in accordance with the selecting.

In yet another aspect, another system is disclosed. The system mayinclude means for receiving a signal associated with a reflection, by anobject, of a light pulse emitted by a LIDAR device of an autonomousvehicle. The system may also include means for calculating a firstdistance to the object based on a first time, the first timecorresponding to a prior light pulse emitted by the LIDAR device of theautonomous vehicle. The system may additionally include means forcalculating a second distance to the object based on a second time, thesecond time corresponding to a different prior light pulse emitted bythe LIDAR device of the autonomous vehicle. The system may furtherinclude means for operating an autonomous vehicle based on a selectionbetween the first distance and second distance.

These as well as other aspects, advantages, and alternatives will becomeapparent to those of ordinary skill in the art by reading the followingdetailed description with reference where appropriate to theaccompanying drawings. Further, it should be understood that thedescription provided in this summary section and elsewhere in thisdocument is intended to illustrate the claimed subject matter by way ofexample and not by way of limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a LIDAR device, according to anexample embodiment.

FIG. 2A illustrates a LIDAR device, according to an example embodiment.

FIG. 2B illustrates another LIDAR system, according to an exampleembodiment.

FIG. 3A shows several views of a LIDAR device being positioned on top ofa vehicle, according to an example embodiment.

FIG. 3B shows emission of light by a LIDAR device positioned on top ofthe vehicle, according to an example embodiment.

FIG. 3C shows detection of reflected light by a LIDAR device positionedon top of the vehicle, according to an example embodiment.

FIG. 3D shows a scanning range of a LIDAR device positioned on top ofthe vehicle, according to an example embodiment.

FIG. 4A shows a nominal unambiguous detection range of a LIDAR devicepositioned on top of the vehicle, according to an example embodiment.

FIG. 4B shows a pulse reflected off an object positioned within anominal unambiguous detection range of a LIDAR device, according to anexample embodiment.

FIG. 4C shows a pulse reflected off an object positioned outside anominal unambiguous detection range of a LIDAR device, according to anexample embodiment.

FIG. 5A shows a first emission time sequence that does not includeapplication of dither and also shows multiple possible detection timesfor each of a plurality of detected return lights pulses, according toan example embodiment.

FIG. 5B shows range ambiguity with respect to the first emission timesequence, according to an example embodiment.

FIG. 6 is a flowchart illustrating a method for disambiguating betweenranges associates with detected return light pulses, according to anexample embodiment.

FIG. 7A shows a second emission time sequence that includes applicationof dither and also shows multiple possible detection times for each of aplurality of detected return lights pulses, according to an exampleembodiment.

FIG. 7B shows selection of ranges to use for object detection, accordingto an example embodiment.

FIG. 8A shows a third emission time sequence that does not includeapplication of dither, according to an example embodiment.

FIG. 8B shows range ambiguity with respect to the third emission timesequence, according to an example embodiment.

FIG. 9A shows a fourth emission time sequence that includes applicationof dither, according to an example embodiment.

FIG. 9B shows mitigation of range ambiguity due to the fourth emissiontime sequence, according to an example embodiment.

FIG. 10 is a flowchart illustrating a method for detecting an objectpositioned outside a nominal unambiguous detection range of a LIDARdevice, according to an example embodiment.

FIG. 11A shows comparison of detection times relative to precedingemission times, according to an example embodiment.

FIG. 11B shows detection of a distant object positioned outside anominal unambiguous detection range of a LIDAR device, according to anexample embodiment.

FIG. 12 is a flowchart illustrating a method for disambiguating betweenmultiple return light pulses detected during the same detection period,according to an example embodiment.

FIG. 13A shows another comparison of detection times relative topreceding emission times, according to an example embodiment.

FIG. 13B shows selection of ranges to use for object detection,according to an example embodiment.

FIG. 14A shows yet another comparison of detection times relative topreceding emission times, according to an example embodiment.

FIG. 14B shows another selection ranges to use for object detection,according to an example embodiment.

FIG. 15 is a flowchart illustrating a method for operating an autonomousvehicle based on a selected distance, according to an exampleembodiment.

FIG. 16 illustrates operation of a vehicle based on scans of anenvironment received from a LIDAR device, according to an exampleembodiment.

FIG. 17 is a simplified block diagram of a vehicle, according to anexample embodiment.

DETAILED DESCRIPTION

Exemplary methods and systems are described herein. It should beunderstood that the word “exemplary” is used herein to mean “serving asan example, instance, or illustration.” Any implementation or featuredescribed herein as “exemplary” or “illustrative” is not necessarily tobe construed as preferred or advantageous over other implementations orfeatures. In the figures, similar symbols typically identify similarcomponents, unless context dictates otherwise. The exampleimplementations described herein are not meant to be limiting. It willbe readily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are contemplatedherein.

I. OVERVIEW

There are continued efforts to improve autonomous operation in which avehicle navigates through an environment with little or no input from adriver. Such efforts include development of vehicles equipped withremote sensing capabilities and possibly accident-avoidance systems. Forinstance, various sensors, such as a LIDAR device, may be included in avehicle to detect objects in an environment of the vehicle and tothereby facilitate autonomous operation and/or accident avoidance.

Generally, a LIDAR device can help estimate distance(s) to environmentalfeatures while scanning through a scene to assemble a “point cloud”indicative of reflective surfaces in the environment. Individual pointsin the point cloud can be determined by emitting a light pulse anddetecting a returning light pulse, if any, reflected from an object inthe environment, and determining the distance to the object according tothe time delay between the emitted light pulse and the detection of thereflected returning light pulse. A LIDAR can include laser(s) or otherlight sources. The laser(s), or the LIDAR as a whole, can rapidly andrepeatedly scan across a scene to provide continuous real-timeinformation on distances to reflective objects in the scene. With thisarrangement, combining the measured distances and the orientation of thelaser(s) while measuring each distance allows for associating athree-dimensional position with each returning light pulse. In this way,a three-dimensional map of points indicative of locations of reflectivefeatures in the environment can be generated for the entire scanningzone.

When a computing system (e.g., in a vehicle) operates a LIDAR device,the computing system may operate the LIDAR device to emit and detectlight pulses in accordance with certain timing. For example, thecomputing system may operate the LIDAR device to emit light pulses atemission times in accordance with an emission time sequence, such as aperiodic sequence (e.g., emission of a light pulse once everymicrosecond). In this example, the computing system may also operate theLIDAR device to detect return light pulses in accordance with adetection time sequence. The detection time sequence may have adetection period intended to detect light pulses returned from an objectlocated within a certain range of the LIDAR. This detection period maybe referred to herein as the corresponding detection period or thenominal detection period or the default detection period, and this rangemay be referred to herein as the nominal unambiguous detection range ornominal detection range. For instance, a corresponding detection periodfor a given light pulse may begin immediately following or at some timeafter emission of that given light pulse, and may end before or afteremission of a subsequent light pulse. This corresponding detectionperiod could be arranged for detection of a return light pulse thatcorresponds to the given emitted light pulse reflecting off an objectlocated within the nominal detection range of the LIDAR to result inthat corresponding return light pulse. The nominal detection range spansa minimum distance, x₀, to a maximum distance x_(m), from the LIDAR. Theminimum distance, x₀, may be 0 meters and maximum distance x_(m), may be60 meters, for example. In other instances, the minimum distance, x₀,may be a distance >0 m away from the LIDAR where object detection isunlikely or would not be an input in the maneuvering of the vehicle, forexample. For example, if the LIDAR is mounted beneath an aircraft, x₀may be 2 meters. Other distances are also contemplated.

In one embodiment, when the LIDAR device detects return light pulses,the computing system could generate a range hypothesis for each detectedlight pulse. Specifically, the computing system may determine, for eachdetected light pulse, a range hypothesis according to a time delayrelative to an emission time of a most recently emitted light pulse.This range hypothesis may be referred to herein as the close rangehypothesis or the default range hypothesis.

A light pulse that is reflected off an object positioned outside thenominal detection range would not be detected by the LIDAR device withinthe nominal detection period. In some cases, the LIDAR device may notdetect such a light pulse if the light pulse's intensity issignificantly attenuated before arriving at the LIDAR device, amongother possibilities.

In some situations, however, the LIDAR device may nonetheless detect alight pulse that is reflected off an object positioned outside thenominal detection range. For example, the object at issue may be aretroreflective object (e.g., a large freeway road sign) positionedbeyond the nominal detection range. When a light pulse reflects off aretroreflective object located beyond the nominal detection range, thereturn light pulse may be detected by the LIDAR device during adetection period after than the nominal detection period, giving rise torange aliasing or range ambiguity. In another example, the object atissue may be an object positioned closer to the LIDAR device than thenominal detection range's minimal distance. Consequently, in somescenarios, when a light pulse reflects off that closer object, the LIDARdevice may detect that light pulse during a detection period before thenominal detection period, also giving rise to range aliasing.

To help with this problem, the computing system could apply apseudo-random dither to respective emission timing of some, but not all,emitted light pulses, so as to respectively shift each such respectiveemission timing away from periodicity by a pseudo-random duration. Withthis arrangement, if the LIDAR device detects light pulses thatreflected off object(s) positioned within the nominal detection rangeand the computing system generates a close range hypothesis based onthese detections, the close range hypothesis could still resemble aknown object and thus the computing system could still end up using thisclose range hypothesis for object detection. However, if the LIDARdevice detects light pulses that reflected off object(s) positionedoutside the nominal detection range and the computing system generates aclose range hypothesis based on these detections, the close rangehypothesis may not resemble a known object due to the above-mentionedpseudo-random shifts (e.g., the ranges of the close range hypothesis maybe substantially different from one another). Therefore, the computingsystem could determine that the close range hypothesis is incorrect andmay not use this close range hypothesis for that set of light pulses forobject detection.

Although application of pseudo-random dither could allow the computingsystem to determine whether or not to use a close range hypothesis forobject detection, it may still be unclear in various situations whichrange(s) to use as basis for object detection. For instance, when lightpulses reflect off an object positioned outside the nominal detectionrange, the computing system could discount the close range hypothesis,but still may not determine the range(s) associated with that object,and thus may not detect that object even though detection of that objectbefore it enters LIDAR's the nominal detection range may be useful.

In accordance with one exemplary embodiment of this disclosure, to helpresolve range ambiguity, a computing system could operate a LIDAR deviceto emit light pulses in accordance with a time sequence that includes atime-varying dither, and, once return light pulses are detected, couldgenerate and evaluate multiple range hypotheses. As such, disclosed aremethods and systems for generating multiple range hypotheses and forusing these range hypotheses for determining the appropriate or higherconfidence or higher likelihood range(s) to use as basis for objectdetection.

In some examples, one of the range hypotheses could be a close rangehypotheses, and the computing system could generate one or morealternate range hypotheses in addition to the close range hypothesis. Inother examples, instead of generating a close range hypothesis, thecomputing system could generate two or more alternate range hypotheses.

Various alternate range hypotheses are possible. By way of example, foreach detected light pulse, the computing system could determine a rangebased on the difference between the detection time and a time a lightpulse was emitted prior to the last emitted light pulse. In thisexample, the alternate range hypothesis could be referred to as a farrange hypothesis, as the determined range correspond to the possibilityof an object being positioned beyond the maximum unambiguous detectionrange.

As such, when the computing system determines that the LIDAR devicedetected return light pulses during two or more detection periods, thecomputing system may determine (i) a first set of ranges in accordancewith a time delay relative to corresponding emission times of aplurality of first emitted light pulses and (ii) a second set of rangesin accordance with a time delay relative to corresponding emission timesof a plurality of second emitted light pulses.

Based on one or more factors, the computing system could then selectbetween using the first set of ranges as a basis for object detectionand using the second set of ranges as a basis for object detection. Forexample, the computing system may determine that the first set of rangesclosely resembles a known object and that the second set of ranges doesnot resemble any known objects, and the system may responsively selectthe first set of ranges to be used as basis for object detection. Inanother example, the system may determine that the second set includesranges that are substantially similar to one another and that the firstset include ranges that are substantially different from one another,and the system may responsively select the second set of ranges to beused as basis for object detection.

In this way, the computing system may determine the appropriate rangesto use for basis for object detection, even when detected return lightpulse(s) are light pulses that reflect off an object positioned outsidethe nominal detection range, and therefore correspond to light pulse(s)emitted prior to the most recently emitted light pulse, for example.

II. EXAMPLE ARRANGEMENT OF A LIDAR DEVICE

Referring now to the Figures, FIG. 1 is a simplified block diagram of aLIDAR device 100, according to an example embodiment. As shown, theLIDAR device 100 includes a power supply arrangement 102, electronics104, light source(s) 106, at least one transmitter 108, at least onereceiver 110, a rotating platform 112, actuator(s) 114, a stationaryplatform 116, a connector arrangement 118, a rotary link 120, and ahousing 122. In other embodiments, the LIDAR device 100 may includemore, fewer, or different components. Additionally, the components shownmay be combined or divided in any number of ways.

Power supply arrangement 102 may be configured to supply power tovarious components of the LIDAR device 100. In particular, the powersupply arrangement 102 may include or otherwise take the form of atleast one power source disposed within the LIDAR device 100 andconnected to various components of the LIDAR device 100 in any feasiblemanner, so as to supply power to those components. Additionally oralternatively, the power supply arrangement 102 may include or otherwisetake the form of a power adapter or the like that is configured toreceive power from one or more external power sources (e.g., from apower source arranged in a vehicle to which the LIDAR device 100 iscoupled) and to supply that received power to various components of theLIDAR device 100 in any feasible manner. In either case, any type ofpower source may be used such as, for example, a battery.

Electronics 104 may include one or more electronic components and/orsystems each arranged to help facilitate certain respective operationsof the LIDAR device 100. In practice, these electronics 104 may bedisposed within the LIDAR device 100 in any feasible manner. Forinstance, at least some of the electronics 104 may be disposed within acentral cavity region of the rotary link 120. Nonetheless, theelectronics 104 may include various types of electronic componentsand/or systems.

For example, the electronics 104 may include various wirings used fortransfer of control signals from a computing system to variouscomponents of the LIDAR device 100 and/or for transfer of data fromvarious components of the LIDAR device 100 to the computing system.Generally, the data that the computing system receives may includesensor data based on detections of light by the receiver 110, amongother possibilities. Moreover, the control signals sent by the computingsystem may operate various components of the LIDAR device 100, such asby controlling emission of light by the transmitter 106, controllingdetection of light by the receiver 110, and/or controlling theactuator(s) 114 to rotate the rotating platform 112, among otherpossibilities.

In some arrangements, the electronics 104 may also include a computingsystem. This computing system may have one or more processors, datastorage, and program instructions stored on the data storage andexecutable by the one or more processor to facilitate variousoperations. With this arrangement, the computing system may thus beconfigured to carry operations described herein, such as those ofmethods described below. Additionally or alternatively, the computingsystem may communicate with an external computing system, controlsystem, or the like (e.g., a computing system arranged in a vehicle towhich the LIDAR device 100 is coupled) so as to help facilitate transferof control signals and/or data between the external system and variouscomponents of the LIDAR device 100.

In other arrangements, however, the electronics 104 may not include acomputing system. Rather, at least some of the above-mentioned wiringsmay be used for connectivity to an external computing system. With thisarrangement, the wirings may help facilitate transfer of control signalsand/or data between the external computing system and the variouscomponents of the LIDAR device 100. Other arrangements are possible aswell.

Further, one or more light sources 106 can be configured to emit,respectively, a plurality of light beams and/or pulses havingwavelengths within a wavelength range. The wavelength range could, forexample, be in the ultraviolet, visible, and/or infrared portions of theelectromagnetic spectrum. In some examples, the wavelength range can bea narrow wavelength range, such as provided by lasers.

In practice, one of the light sources 106 may be a laser diodeconfigured to emit pulses of light. In particular, a laser diode may bea semiconductor device including a p-n junction with an active region inwhich oppositely polarized, energized charge carriers (e.g., freeelectrons and/or holes) recombine while current flows through the deviceacross the p-n junction. The recombination results in emission of lightdue to a change in energy state of the charge carriers. When the activeregion is heavily populated by such energized pairs (e.g., the activeregion may have a population inversion of energized states), stimulatedemission across the active region may produce a substantially coherentwave front of light that is then emitted from the laser diode.Recombination events, and the resulting light emission, occur inresponse to current flowing through the device, and so applying a pulseof current to the laser diode results in emission of a pulse of lightfrom the laser diode.

As such, the present disclosure will be generally described herein inthe context of a laser diode being used as the primary light source 106.In some arrangements, however, the one or more light sources 106 mayadditionally or alternatively include fiber lasers, light emittingdiodes (LED), vertical cavity surface emitting lasers (VCSEL), organiclight emitting diodes (OLED), polymer light emitting diodes (PLED),light emitting polymers (LEP), liquid crystal displays (LCD),microelectromechanical systems (MEMS), and/or any other deviceconfigured to selectively transmit, reflect, and/or emit light toprovide the plurality of emitted light beams and/or pulses.

Furthermore, transmitter 108 may be configured to emit light into anenvironment. In particular, the transmitter 108 may include an opticalarrangement that is arranged to direct light from a light source 106toward the environment. This optical arrangement may include anyfeasible combination of mirror(s) used to guide propagation of the lightthroughout physical space and/or lens(es) used to adjust certaincharacteristics of the light, among other optical components. Forinstance, the optical arrangement may include a transmit lens arrangedto collimate the light, thereby resulting in light having rays that aresubstantially parallel to one another. Moreover, the lens may be shapedto spread or otherwise scatter light in a particular manner, such as bycausing the vertical light spread of +7° away from a horizontal axis to−18° away from the horizontal axis (e.g., the horizontal axis ideallybeing parallel to a ground surface in the environment) for example.

As noted, the LIDAR device 100 may include at least one receiver 110.The receiver 110 may be respectively configured to at least detect lighthaving wavelengths in the same wavelength range as the one of the lightemitted from the transmitter 108. In doing so, the receiver 110 maydetect light with a particular resolution. For example, the receiver 110may be configured to detect light with a 0.036° (horizontal)×0.067°(vertical) angular resolution. Moreover, the receiver 110 may beconfigured to scan the environment with a particular FOV. For example,the receiver 110 may be arranged to focus incoming light within a rangeof +7° away from the above-mentioned horizontal axis to −18° away fromthe horizontal axis. In this way, the receiver 110 allows for detectionof light along a range of +7° to −18°, which matches the above-mentionedexemplary vertical spread of emitted light that the transmitter 108provides. It is noted that this resolution and FOV are described forexemplary purposes only and are not meant to be limiting.

In an example implementation, the receiver 110 may have an opticalarrangement that allows the receiver 110 to provide the resolution andFOV as described above. Generally, such an optical arrangement may bearranged to provide an optical path between at least one optical lensand a photodetector array.

More specifically, the receiver 110 may include an optical lens arrangedto focus light reflected from one or more objects in the environment ofthe LIDAR device 100 onto detectors of the receiver 110. To do so, theoptical lens may have certain dimensions (e.g., approximately 10 cm×5cm) as well as a certain focal length (e.g., approximately 35 cm).Moreover, the optical lens may be shaped so as to focus incoming lightalong a particular vertical FOV as described above (e.g., +7° to −18°).Such shaping of the first receiver's optical lens may take on one ofvarious forms (e.g., spherical shaping) without departing from the scopeof the present disclosure.

Furthermore, as noted, the receiver 110 may have a photodetector array,which may include two or more detectors each configured to convertdetected light (e.g., in the above-mentioned wavelength range) into anelectrical signal indicative of the detected light. In practice, such aphotodetector array could be arranged in one of various ways. Forexample, the detectors can be disposed on one or more substrates (e.g.,printed circuit boards (PCBs), flexible PCBs, etc.) and arranged todetect incoming light that is traveling along the optical path from theoptical lens. Also, such a photodetector array could include anyfeasible number of detectors aligned in any feasible manner. Forexample, the photodetector array may include a 13×16 array of detectors.It is noted that this photodetector array is described for exemplarypurposes only and is not meant to be limiting.

Generally, the detectors of the array may take various forms. Forexample, the detectors may take the form of photodiodes, avalanchephotodiodes (e.g., geiger mode and/or linear mode avalanchephotodiodes), phototransistors, cameras, active pixel sensors (APS),charge coupled devices (CCD), cryogenic detectors, and/or any othersensor of light configured to receive focused light having wavelengthsin the wavelength range of the emitted light. Other examples arepossible as well.

Further, as noted, the LIDAR device 100 may include a rotating platform112 that is configured to rotate about an axis. In order to rotate inthis manner, one or more actuators 114 may actuate the rotating platform112. In practice, these actuators 114 may include motors, pneumaticactuators, hydraulic pistons, and/or piezoelectric actuators, amongother possibilities.

In an example implementation, the transmitter 108 and the receiver 110may be arranged on the rotating platform 112 such that each of thesecomponents moves relative to the environment based on rotation of therotating platform 112. In particular, each of these components could berotated relative to an axis so that the LIDAR device 100 may obtaininformation from various directions. In this manner, the LIDAR device100 may have a horizontal viewing direction that can be adjusted byactuating the rotating platform 112 to different directions.

With this arrangement, a computing system could direct an actuator 114to rotate the rotating platform 112 in various ways so as to obtaininformation about the environment in various ways. In particular, therotating platform 112 could rotate at various extents and in eitherdirection. For example, the rotating platform 112 may carry out fullrevolutions such that the LIDAR device 100 provides a 360° horizontalFOV of the environment. Thus, given that the receiver 110 may rotatebased on rotation of the rotating platform 112, the receiver 110 mayhave a horizontal FOV (e.g., 360° or less) and also a vertical FOV asdescribed above.

Moreover, the rotating platform 112 could rotate at various rates so asto cause LIDAR device 100 to scan the environment at various refreshrates. For example, the LIDAR device 100 may be configured to have arefresh rate of 15 Hz (e.g., fifteen complete rotations of the LIDARdevice 100 per second). In this example, assuming that the LIDAR device100 is coupled to a vehicle as further described below, the scanningthus involves scanning a 360° FOV around the vehicle fifteen times everysecond. Other examples are also possible. For example, the rotatingplatform 112 could swivel the LIDAR device so that it scans back andforth within a smaller angle horizontal FOV.

Yet further, as noted, the LIDAR device 100 may include a stationaryplatform 116. In practice, the stationary platform 116 may take on anyshape or form and may be configured for coupling to various structures,such as to a top of a vehicle for example. Also, the coupling of thestationary platform 116 may be carried out via any feasible connectorarrangement 118 (e.g., bolts, screws, and/or adhesives). In this way,the LIDAR device 100 could be coupled to a structure so as to be usedfor various purposes, such as those described herein.

Furthermore, the LIDAR device 100 may also include a rotary link 120that directly or indirectly couples the stationary platform 116 to therotating platform 112. Specifically, the rotary link 120 may take on anyshape, form and material that provides for rotation of the rotatingplatform 112 about an axis relative to the stationary platform 116. Forinstance, the rotary link 120 may take the form of a shaft or the likethat rotates based on actuation from an actuator 114, therebytransferring mechanical forces from the actuator 114 to the rotatingplatform 112. Moreover, as noted, the rotary link 120 may have a centralcavity in which electronics 104 and/or one or more other components ofthe LIDAR device 100 may be disposed. Other arrangements are possible aswell.

Yet further, as noted, the LIDAR device 100 may include a housing 122.In practice, the housing 122 may take on any shape and form. Forexample, the housing 122 can be a dome-shaped housing, among otherpossibilities. Moreover, the housing 122 may be arranged in various waysrelative to other components of the LIDAR device 100. It is noted thatthis housing is described for exemplary purposes only and is not meantto be limiting.

In an example implementation, the housing 122 may be coupled to therotating platform 112 such that the housing 122 is configured to rotateabout the above-mentioned axis based on rotation of the rotatingplatform 112. With this implementation, the transmitter 108, thereceiver 110, and possibly other components of the LIDAR device 100 mayeach be disposed within the housing 122. In this manner, the transmitter108 and the receiver 110 may rotate along with this housing 122 whilebeing disposed within the housing 122.

Moreover, the housing 122 may have an aperture formed thereon, whichcould take on any feasible shape and size. In this regard, thetransmitter 108 could be arranged within the housing 122 so as to emitlight into the environment through the aperture. In this way, thetransmitter 108 may rotate along with the aperture due to correspondingrotation of the housing 122, thereby allowing for emission of light intovarious directions. Also, the receiver 110 could be arranged within thehousing 122 so as to detect light that enters the housing 122 from theenvironment through the aperture. In this way, the receiver 110 mayrotate along with the aperture due to corresponding rotating of thehousing 122, thereby allowing for detection of the light incoming fromvarious directions along the horizontal FOV.

Yet further, the housing 122 may be composed of a material that is atleast partially non-transparent, except for the aperture, which could becomposed of a transparent material. In this way, light could propagatethrough the aperture, thereby allowing for scanning of the environment.But due to the housing 122 being at least partially non-transparent, thehousing 122 may block at least some light from entering the interiorspace of the housing 122 and thus may help mitigate thermal effects. Forinstance, the housing 122 may block sun rays from entering the interiorspace of the housing 122, which may help avoid overheating of variouscomponents of the LIDAR device 100 due to those sun rays. Moreover, dueto various components of the LIDAR device 100 being disposed within thehousing 122 and due to the housing 122 rotating along with thosecomponents, the housing 122 may help protect those components fromvarious environmental hazards, such as rain and/or snow, among others.

In other implementations, however, the housing 122 may be an exteriorstationary housing that does not rotate with the LIDAR device 100. Forexample, the exterior stationary housing could be coupled to a vehicleand the LIDAR device could also be coupled to the vehicle while beingconfigured to rotate within the exterior stationary housing. In thissituation, the exterior stationary housing would likely be transparentso as to allow for propagation of light through the exterior stationaryhousing and thus for scanning of the environment by the LIDAR device100. Moreover, the LIDAR device 100 may also include an aperture throughwhich light may propagate and such an aperture may be on an interiorhousing of the LIDAR device 100, which may rotate within the exteriorstationary housing along with other components of the LIDAR device 100.Other implementations are possible as well.

III. ILLUSTRATIVE IMPLEMENTATION OF THE LIDAR DEVICE

FIG. 2A illustrates a LIDAR device 200, according to an exampleembodiment. LIDAR 200 may be similar to LIDAR 100. For example, asshown, LIDAR device 200 includes a lens 208, a rotating platform 216, astationary platform 220, and a housing 224 which may be similar,respectively, to optical element 108, rotating platform 216, stationaryplatform 120, and housing 124. Additionally, as shown, light beams 280emitted by LIDAR device 200 propagate from lens 108 along a pointingdirection of LIDAR 200 toward an environment of LIDAR device 200, andreflect off one or more objects in the environment as reflected light290.

In some examples, housing 224 can be configured to have a substantiallycylindrical shape and to rotate about an axis of LIDAR device 200. Inone example, housing 224 can have a diameter of approximately 10centimeters. Other examples are possible. In some examples, the axis ofrotation of LIDAR device 200 is substantially vertical. For instance, byrotating housing 224 that includes the various components athree-dimensional map of a 360-degree view of the environment of LIDARdevice 200 can be determined. Additionally or alternatively, in someexamples, LIDAR device 200 can be configured to tilt the axis ofrotation of housing 224 to control a field of view of LIDAR device 200.Thus, in some examples, rotating platform 216 may comprise a movableplatform that may tilt in one or more directions to change the axis ofrotation of LIDAR device 200.

In some examples, lens 208 can have an optical power to both collimatethe emitted light beams 280, and focus the reflected light 290 from oneor more objects in the environment of LIDAR device 200 onto detectors inLIDAR device 200. In one example, lens 208 has a focal length ofapproximately 120 mm. Other example focal lengths are possible. By usingthe same lens 208 to perform both of these functions, instead of atransmit lens for collimating and a receive lens for focusing,advantages with respect to size, cost, and/or complexity can beprovided. Alternatively, LIDAR 200 may include separate transmit andreceive lenses.

FIG. 2B illustrates another possible implementation of a LIDAR system,according to an example embodiment. As shown, a LIDAR system 228 couldinclude a first LIDAR 230, a second LIDAR 232, a dividing structure 234,and light filter 236.

In some examples, the first LIDAR 230 may be configured to scan anenvironment around a vehicle by rotating about an axis (e.g., verticalaxis, etc.) continuously while emitting one or more light pulses anddetecting reflected light pulses off objects in the environment of thevehicle, for example. In some embodiments, the first LIDAR 230 may beconfigured to repeatedly rotate about the axis to be able to scan theenvironment at a sufficiently high refresh rate to quickly detect motionof objects in the environment. For instance, the first LIDAR 230 mayhave a refresh rate of 10 Hz (e.g., ten complete rotations of the firstLIDAR 230 per second), thereby scanning a 360-degree FOV around thevehicle ten times every second. Through this process, for instance, a 3Dmap of the surrounding environment may be determined based on data fromthe first LIDAR 230. In one embodiment, the first LIDAR 230 may includea plurality of light sources that emit 64 laser beams having awavelength of 905 nm. In this embodiment, the 3D map determined based onthe data from the first LIDAR 230 may have a 0.2° (horizontal)×0.3°(vertical) angular resolution, and the first LIDAR 230 may have a 360°(horizontal)×20° (vertical) FOV of the environment. In this embodiment,the 3D map may have sufficient resolution to detect or identify objectswithin a medium range of 100 meters from a vehicle, for example.However, other configurations (e.g., number of light sources, angularresolution, wavelength, range, etc.) are possible as well.

Unlike the first LIDAR 230, in some embodiments, the second LIDAR 232may be configured to scan a narrower FOV of the environment around avehicle. For instance, the second LIDAR 232 may be configured to rotate(horizontally) for less than a complete rotation about a similar axis.Further, in some examples, the second LIDAR 232 may have a lower refreshrate than the first LIDAR 230. Through this process, a vehicle maydetermine a 3D map of the narrower FOV of the environment using the datafrom the second LIDAR 232. The 3D map in this case may have a higherangular resolution than the corresponding 3D map determined based on thedata from the first LIDAR 230, and may thus allowdetection/identification of objects that are further than the mediumrange of distances of the first LIDAR 230, as well as identification ofsmaller objects within the medium range of distances. In one embodiment,the second LIDAR 232 may have a FOV of 8° (horizontal)×15° (vertical), arefresh rate of 4 Hz, and may emit one narrow beam having a wavelengthof 1550 nm. In this embodiment, the 3D map determined based on the datafrom the second LIDAR 232 may have an angular resolution of 0.1°(horizontal)×0.03° (vertical), thereby allowing detection/identificationof objects within a range of around three hundred meters from a vehicle.However, other configurations (e.g., number of light sources, angularresolution, wavelength, range, etc.) are possible as well.

In some examples, a vehicle may be configured to adjust a viewingdirection of the second LIDAR 232. For example, while the second LIDAR232 has a narrow horizontal FOV (e.g., 8 degrees), the second LIDAR 232may be mounted to a stepper motor (not shown) that allows adjusting theviewing direction of the second LIDAR 232 to pointing directions otherthan that shown in FIG. 1B. Thus, in some examples, the second LIDAR 232may be steerable to scan the narrow FOV along any pointing directionfrom a vehicle.

The dividing structure 234 may be formed from any solid materialsuitable for supporting the first LIDAR 230 and/or optically isolatingthe first LIDAR 230 from the second LIDAR 232. Example materials mayinclude metals, plastics, foam, among other possibilities.

The light filter 236 may be formed from any material that issubstantially transparent to light having wavelengths with a wavelengthrange, and substantially opaque to light having wavelengths outside thewavelength range. For example, the light filter 236 may allow lighthaving the first wavelength of the first LIDAR 230 (e.g., 905 nm) andthe second wavelength of the second LIDAR 232 (e.g., 1550 nm) topropagate through the light filter 236. As shown, the light filter 236is shaped to enclose the first LIDAR 230 and the second LIDAR 232. Thus,in some examples, the light filter 236 may also be configured to preventenvironmental damage to the first LIDAR 230 and the second LIDAR 232,such as accumulation of dust or collision with airborne debris, amongother possibilities. In some examples, the light filter 236 may beconfigured to reduce visible light propagating through the light filter236. In turn, the light filter 236 may improve an aesthetic appearanceof a vehicle by enclosing the first LIDAR 230 and the second LIDAR 232,while reducing visibility of the components of the sensor unit 228 froma perspective of an outside observer, for example. In other examples,the light filter 236 may be configured to allow visible light as well asthe light from the first LIDAR 230 and the second LIDAR 232.

In some embodiments, portions of the light filter 236 may be configuredto allow different wavelength ranges to propagate through the lightfilter 236. For example, an upper portion of the light filter 236 abovethe dividing structure 234 may be configured to allow propagation oflight within a first wavelength range that includes the first wavelengthof the first LIDAR 230. Further, for example, a lower portion of thelight filter 236 below the dividing structure 234 may be configured toallow propagation of light within a second wavelength range thatincludes the second wavelength of the second LIDAR 232. In otherembodiments, the wavelength range associated with the light filter 236may include both the first wavelength of the first LIDAR 230 and thesecond wavelength of the second LIDAR 232.

FIGS. 3A to 3D next collectively illustrate implementation of a LIDARdevice in a vehicle 300, specifically illustrating an implementation ofthe example LIDAR device 200 in the vehicle 300. Although vehicle 300 isillustrated as a car, other embodiments are possible. Furthermore,although the example vehicle 300 is shown as a vehicle that may beconfigured to operate in autonomous mode, the embodiments describedherein are also applicable to vehicles that are not configured tooperate autonomously. Thus, the example vehicle 300 is not meant to belimiting.

In particular, FIG. 3A shows a Right Side View, Front View, Back View,and Top View of the vehicle 300. As shown, the vehicle 300 includes theLIDAR device 200 being positioned on a top side of the vehicle 300opposite a bottom side on which wheels 302 of the vehicle 300 arelocated. Although the LIDAR device 200 is shown and described as beingpositioned on the top side of the vehicle 300, the LIDAR device 200could be positioned on any part feasible portion of the vehicle withoutdeparting from the scope of the present disclosure.

Moreover, FIGS. 3B to 3C next show that the LIDAR device 200 may beconfigured to scan an environment around the vehicle 300 (e.g., at arefresh rate of 15 Hz) by rotating about a vertical axis 308 whileemitting one or more light pulses and detecting reflected light pulsesoff objects in the environment of the vehicle 300, for example.

More specifically, FIG. 3B shows that the LIDAR device 200 emits lightwith the above-mentioned vertical spread of +7° to −18°. In this way,the light emissions can be emitted toward regions of the environmentthat are relatively close to the vehicle 300 (e.g., a lane marker)and/or towards regions of the environment that are further away from thevehicle 300 (e.g., a road sign ahead of the vehicle).

Further, FIG. 3C shows that the LIDAR device 200 may detect reflectedlight with the above-mentioned vertical FOV of +7° to −18° and do so ata resolution of 0.036°×0.067°. In this way, the LIDAR device 200 maydetect light reflected off regions of the environment that arerelatively close to the vehicle 300 and/or light reflected off regionsof the environment that are further away from the vehicle 300.

Generally, these detection distances are illustrated by way of examplein FIG. 3D. In particular, FIG. 3D illustrates a top view of the vehicle300 in the above-described scenario where the vehicle 300 uses the LIDARdevice 200 for scanning a surrounding environment. Accordingly, thehorizontal FOV of the LIDAR device 200 may span 360° in all directionsaround the vehicle 300.

As shown in FIG. 3D, the LIDAR device 200 may be suitable for detectionand/or identification of objects within a range of distances to thevehicle 300. More specifically, objects outside of contour 304 andwithin a range of distances defined by the contour 306 may be properlydetected/identified using the data from the LIDAR device 200. It isnoted that these contours are not to scale but are illustrated as shownfor convenience of description.

IV. NOMINAL DETECTION RANGE AND RANGE AMBIGUITY

Given that a LIDAR device may be suitable for detection of objectswithin a range of distances, the LIDAR device may have a nominaldetection range that spans from a minimum detection range to a maximumunambiguous detection range. For a given detection period of the LIDARdevice, the maximum unambiguous detection range may define the greatestdistance at which an object can be positioned away from the LIDAR deviceand be detected by the LIDAR device within a designated detectionperiod, e.g., the nominal detection period. Signals reflected fromobjects past the maximum unambiguous detection range may be tooattenuated to be reliably detected. The minimum detection range maydefine the minimum distance at which an object should be positioned awayfrom the LIDAR device in order to be detected by the LIDAR device withinthe designated detection period. Signals reflected from objects closerthan the minimum distance may return to the LIDAR device before thedesignated detection period begins.

More specifically, a computing system may operate the LIDAR device toemit and detect light pulses in accordance with certain timing. Forexample, the computing system may operate the LIDAR device to emit lightpulses at emission times in accordance with an emission time sequence,which could be predefined or pseudo-random. This emission time sequencemay then establish a detection time sequence according to which theLIDAR device detects return light pulses.

For instance, once the computing system operates the LIDAR device toemit a given light pulse, a corresponding detection period for the givenlight pulse may begin immediately following or at some time afteremission of that given light pulse, and may end before or after emissionof a subsequent light pulse, among other options. During thiscorresponding detection period, the LIDAR device could then detect agiven return light pulse that corresponds to the given emitted lightpulse, such as when the given emitted light pulse reflects off an objectwithin the nominal detection range to result in that return light pulse.After the LIDAR device detects the given return light pulse, thecomputing system could then determine a specific range associated withthe given return light pulse according to a time delay relative to theemission time of the given emitted light pulse.

As discussed above, a detection period may establish a nominal detectionrange that spans from a minimum detection range to a maximum unambiguousdetection range.

In particular, the time difference between the emission time of a lightpulse and the end time of the detection period may correspond to amaximum time delay that a return light pulse from that emitted lightpulse could have in order to still be detected by the LIDAR deviceduring the detection period. For instance, if a detection period begins1 nanosecond after emission of a light pulse and ends 400 nanoseconds(ns) after emission of that light pulse, in order for a return lightpulse from that emitted light pulse to be detected by the LIDAR deviceduring the nominal detection period, this light pulse should return tothe LIDAR device within 400 ns. Further, because a computing systemcould determine a distance to an object according to a time delaybetween an emitted light pulse and detection of a reflected returninglight pulse, the maximum time delay may establish the greatest distanceat which an object could be positioned away from the LIDAR device, suchthat the LIDAR device could still detect during the detection period alight pulse that reflected off this object and then returned to theLIDAR. Generally, this greatest distance may define the maximumunambiguous detection range for the emitted light pulse.

Additionally, the time difference between emission time of a light pulseand the start time of the detection period may correspond to a minimumtime delay that a return light pulse should have in order to be detectedby the LIDAR device during the nominal detection period. For instance,if a detection period starts 50 nanoseconds (ns) after emission of alight pulse, in order for a return light pulse to be detected by theLIDAR device during that detection period after the light pulse isemitted by the LIDAR device, this light pulse may have to return to theLIDAR device after no less than 50 ns. Further, because a computingsystem could determine a distance to an object according to a time delaybetween an emitted light pulse and detection of a reflected returninglight pulse, the minimum time delay may establish the minimum distanceat which an object should be positioned away from the LIDAR device, suchthat the LIDAR device could still detect during the detection period alight pulse that reflected off this object and then returned to theLIDAR. Generally, this minimum distance may define the minimum detectionrange for the detection period.

In some cases, different detection periods could have differentrespective nominal detection ranges. For example, as the duration of adetection period increases, a maximum detection range for the detectionperiod may increase, and vice versa. Thus, detection periods that are oflonger durations may have greater respective maximum unambiguousdetection ranges and detection periods that are of shorter durations mayhave smaller respective maximum unambiguous detection ranges.

Given this, in another aspect, a nominal detection range could definethe distances at which an object can be positioned away from the LIDARdevice and be reliably detected by the LIDAR device when taking alldetection periods of the LIDAR device into consideration. In particular,if a LIDAR device is operated such that each detection period is thesame, that detection period may establish a nominal detection range ofthe LIDAR device. But if a LIDAR device is operated such that some orall detection periods are different compared to one another, then thedetection period that provides for the greatest maximum time delay mayestablish a maximum detection range of the LIDAR device, and thedetection period that provides for the smallest minimum time delay mayestablish a minimum detection range of the LIDAR device.

With this arrangement, if a light pulse is reflected off an objectpositioned outside the nominal detection range, a computing system maynot determine a distance associated with that light pulse or coulddetermine an incorrect distance associated with that light pulse.

By way of example, in many situations, if a light pulse is reflected offan object positioned beyond a maximum unambiguous detection range, theLIDAR device may not detect such a light pulse, as this light pulse mayexperience a significant attenuation in its intensity before arriving atthe LIDAR device. In some situations, however, the LIDAR device maynonetheless detect that returning light pulse. For instance, the objectpositioned beyond the maximum unambiguous detection range may be aretroreflective object, such as a large road sign located beyond themaximum unambiguous detection range. A return light pulse that hasreflected off such a retroreflective object may be detected by the LIDARdevice during a subsequent detection period. As a result, without rangealiasing resilience, the computing system may erroneously determine theretroreflective object is closer than it physically is from the LIDAR incalculating the distance the light traveled based on the emission timeof a later emitted pulse because it was not expected to receive anun-attenuated return signal from an object located past the maximumunambiguous detection range.

In another example, in some situations, if a light pulse is reflectedoff an object positioned closer than a minimum detection range, theLIDAR device may or may not detect such a light pulse. But if the LIDARdevice does detect such a light pulse, that light pulse may arrive atthe LIDAR device before start of the detection period, and thus theLIDAR device may not detect that light pulse in the detection periodassociated with that light pulse. As a result, the computing system maynot determine a distance associated with this light pulse according to atime delay relative to an emission time of that light pulse.

FIGS. 4A-4C illustrate a nominal detection range of the LIDAR device200. In particular, FIGS. 4A-4C show that the LIDAR device 200 may havea nominal detection range that spans from a minimum detection range of 0meters to a maximum unambiguous detection range 400 of 60 meters (60 m).In this example, this maximum unambiguous detection range 400 isestablished by the detection period 408 that starts following anemission time 406A of a light pulse and ends at a subsequent emissiontime 406B of a subsequent light pulse. As shown, the detection period408 has a duration of 400 ns, which leads to the maximum unambiguousdetection range 400 to be at approximately 60 m away from the LIDARdevice 200 (maximum unambiguous detection range*2=speed ofpulse*detection period=˜299,792,458 m/s*400 ns).

Further, FIGS. 4A-4C illustrate that a nearby object 402 (e.g., a nearbyroad sign) could be positioned within the maximum unambiguous detectionrange 400 and that a distant object 404 (e.g., a retroreflective“freeway entrance” road sign) could be positioned outside of the maximumdetection range 400. In this regard, FIG. 4B shows that a pulsereflected off the nearby object 402 would return to the LIDAR device 200before the end of the detection period 408 and would do so at adetection time 410 of 350 ns after the emission time 406A. Thisdetection time 410 corresponds to a range of 52.5 m, which is thedistance at which the nearby object 402 is positioned away from theLIDAR device 200. In contrast, distant object 404 is positioned at adistance of 80 m away from the LIDAR device 200, which is a distancethat exceeds the maximum detection range 400 of 60 m. Therefore, asshown in FIG. 4C, a pulse reflected off the distant object 404 wouldreturn to the LIDAR device 200 after the end of the detection period 408and thus would not be detected by the LIDAR device 200 during thatdetection period 408. Other illustrations are possible as well.

When an emitted light pulse is reflected off a retroreflective objectpositioned beyond the maximum unambiguous detection range, the LIDARdevice may detect this light pulse at a time after the device hasstopped listening for return signal from that emitted light pulse andinstead during a time the device is listening for return signals from asubsequently emitted light pulse, which may lead to range aliasing,thereby leading to false object detection, among other outcomes.

FIGS. 5A to 5B illustrate an example detection of return light pulses.

In particular, FIG. 5A shows light pulses A-F emitted respectively atemission times A-F in accordance with a periodic emission time sequence#1 that does not include application of dither. These periodic emissiontimes establish detection periods A-F each of the same 400 ns duration.As shown, light pulses A-F each reflect off the distant object 404 and,as a result, are each respectively detected during a subsequentdetection period.

Generally, the computing system could determine candidate rangesassociated with detected light pulses A-F without accounting for thepossibility of large retroreflective objects located outside the maximumunambiguous detection range. For instance, the computing system maydetermine that the LIDAR device 200 detected light pulse A at adetection time Tn0 of 133 ns relative to emission time B, whichcorresponds to a range of 20 m as shown in FIG. 5B. And as indicated bydetection times Tn1 to Tn5, a similar approach could be used fordetermining ranges associated with light pulses B-F, thereby resultingin first ranges 502 corresponding to a close range hypothesis of anobject being positioned at 20 m away from the LIDAR device 200.

Given this, the computing system determines ranges 502 that are the sameas one another and, as a result, could determine that these ranges 502should be used as basis for object detection. However, this close rangehypothesis is inaccurate, as light pulses A-F in fact reflected off thedistant object 404 that is positioned beyond the maximum unambiguousdetection range of the LIDAR device 200. Thus, use of this close rangehypothesis for object detection could lead to a false detection of anearby object.

In one embodiment, the computing system may determine that the LIDARdevice 200 detected light pulse A at a detection time Tf0 of 533 nsrelative to emission time A, which corresponds to a range of 80 m asshown in FIG. 5B. And as indicated by detection times Tf1 to Tf5, asimilar approach could be used for determining ranges associated withlight pulses B-F, thereby resulting in second ranges 504 correspondingto a far range hypothesis of an object being positioned at 80 m awayfrom the LIDAR device 200. This far range hypothesis is accurate, aslight pulses A-F in fact reflected off the distant object 404 that ispositioned beyond the maximum detection range of the LIDAR device 200.

In some instances, although this far range hypothesis is accurate, thecomputing system may be unable to disambiguate between the close and farhypothesis if a time-varying dither is not also applied. Specifically,the computing system may determine a close range hypothesis includingthat ranges 502 are the same as one another and that this indicates anobject is positioned at 20 m away from the LIDAR device 200.Additionally, the computing system may determine a far range hypothesisincluding that ranges 504 are the same as one another and that thisindicates an object is positioned at 80 m away from the LIDAR device200. As a result, the computing system may determine that an objectcould be positioned at 20 m away from the LIDAR device 200 or at 80 maway from the LIDAR device 200, but may be unable to determine which ofthese determinations is in fact accurate without additional information,thereby leading to range ambiguity. Additional information that mayallow the computing system to disambiguate between the two ranges couldinclude information that the detected object is likely or unlikely to beof a size that would be detected at the farther distance. For example,if the object is shaped like a sign, it may be possible the object isfarther away. If the object is shaped like a small animal, it may beunlikely. Other illustrations are also possible.

V. USING MULTIPLE RANGE HYPOTHESES AND APPLICATION OF TIME-VARYINGDITHER TO OVERCOME RANGE AMBIGUITY

FIG. 6 is a flowchart illustrating a method 600, according to an exampleimplementation. In particular, method 600 may be implemented to helpresolve range ambiguity encountered in one or more of varioussituations.

Method 600 shown in FIG. 6 (and other processes and methods disclosedherein) presents a method that can be implemented within an arrangementinvolving, for example, the LIDAR device 100 of FIG. 1, vehicle 300shown in FIGS. 3A-3D, and/or vehicle 1700 shown in FIG. 17 and furtherdescribed below (or more particularly by one or more components orsubsystems thereof, such as by a processor and a non-transitorycomputer-readable medium having instructions that are executable tocause the device to perform functions described herein). Additionally oralternatively, method 600 may be implemented within any otherarrangements and systems.

Method 600 and other processes and methods disclosed herein may includeone or more operations, functions, or actions as illustrated by one ormore of blocks 602-610. Although the blocks are illustrated insequential order, these blocks may also be performed in parallel, and/orin a different order than those described herein. Also, the variousblocks may be combined into fewer blocks, divided into additionalblocks, and/or removed based upon the desired implementation.

In addition, for the method 600 and other processes and methodsdisclosed herein, the flowchart shows functionality and operation of onepossible implementation of present implementations. In this regard, eachblock may represent a module, a segment, or a portion of program code,which includes one or more instructions executable by a processor forimplementing specific logical functions or steps in the process. Theprogram code may be stored on any type of computer readable medium, forexample, such as a storage device including a disk or hard drive. Thecomputer readable medium may include non-transitory computer readablemedium, for example, such as computer-readable media that stores datafor short periods of time like register memory, processor cache andRandom Access Memory (RAM). The computer readable medium may alsoinclude non-transitory media, such as secondary or persistent long termstorage, like read only memory (ROM), optical or magnetic disks,compact-disc read only memory (CD-ROM), for example. The computerreadable media may also be any other volatile or non-volatile storagesystems. The computer readable medium may be considered a computerreadable storage medium, for example, or a tangible storage device. Inaddition, for the method 600 and other processes and methods disclosedherein, each block in FIG. 6 may represent circuitry that is wired toperform the specific logical functions in the process.

At block 602, method 600 involves operating a LIDAR device to emit lightpulses at emission times in accordance with an emission time sequence,where the emission time sequence includes a time-varying dither, and todetect return light pulses in accordance with a detection time sequence,where the detection time sequence includes, for each emitted lightpulse, a corresponding detection period for detection of a correspondingreturn light pulse, and where a detection time of a return light pulserelative to a corresponding emission time of a corresponding emittedlight pulse is indicative of a range to an object that reflected thecorresponding emitted light pulse.

As noted, a computing system could operate a LIDAR device to emit anddetect light pulses in accordance with certain timing.

For instance, the computing system could operate the LIDAR device toemit light pulses in accordance with an emission time sequence thatincludes application of a time-varying dither. In practice, applicationof dither may involve pseudo-random deviation of a periodic signal awayfrom periodicity, such as by application of noise to the signal, amongother possibilities. In this regard, the computing system may applypseudo-random dither to respective emission timing of some, but not all,emitted light pulses, so as to respectively shift each such respectiveemission timing away from periodicity by a pseudo-random duration. Withthis implementation, as noted, due to the shifts in periodicity, thecomputing system could potentially discount an incorrect close rangehypothesis.

Furthermore, the emission time sequence may help establish a detectiontime sequence according to which the LIDAR device detects return lightpulses. Generally, this detection time sequence may include acorresponding detection period respectively for each emitted light. Inparticular, a corresponding detection period for a given light pulse maybegin immediately following or at some time after emission of that givenlight pulse, and may end before or after emission a subsequent lightpulse. During this corresponding detection period, the LIDAR devicecould detect a given return light pulse that corresponds to the givenemitted light pulse, such as when the given emitted light pulse reflectsoff an object to result in that return light pulse. After the LIDARdevice detects the given return light pulse at a certain detection time,the computing system could then determine a range to an object thatreflected the given emitted light pulse. As discussed, the computingsystem could determine this range according to a time delay between thedetection time of the given return light pulse and the emission time ofthe given emitted light pulse.

At block 604, method 600 involves making a determination that the LIDARdevice detected return light pulses during corresponding detectionperiods for each of two or more emitted light pulses.

Generally, a computing system could make a determination that the LIDARdevice detected one or more return light pulses respectively during eachof two or more detection periods. For instance, a plurality of emittedlight pulses could each respectively have a corresponding detectionperiod. For each such corresponding detection period, the computingsystem could determine that the LIDAR device detected one or more returnlight pulses. In practice, some or all of these light pulses could belight pulses that reflected off object(s) positioned outside a nominaldetection range of the LIDAR device. Additionally or alternatively, someor all of these light pulses could be light pulses that reflected offnearby object(s) positioned within the nominal detection range.

At block 606, method 600 involves, in response to making thedetermination, determining that (i) the detected return light pulseshave detection times relative to corresponding emission times of aplurality of first emitted light pulses that are indicative of a firstset of ranges and (ii) the detected return light pulses have detectiontimes relative to corresponding emission times of a plurality of secondemitted light pulses that are indicative of a second set of ranges.

Once the computing system determines that the LIDAR device detectedseveral return light pulses, the computing system may responsivelygenerate two or more range hypotheses for these detected return lightpulses, at least one of which would be an alternate range hypothesis.For example, the computing system could generate a close rangehypothesis and one or more alternate range hypotheses. In anotherexample, the computing system could generate two or more alternate rangehypotheses. Other examples are also possible.

When generating a close range hypothesis, the computing system maydetermine a range respectively for each detected return light pulseaccording to a time delay relative to an emission time of a mostrecently emitted light pulse. As discussed, for a given return lightpulse detected during a given detection period, the most recentlyemitted light pulse may be the one that corresponds to the givendetection period during which the given return light pulse was detected.For example, in FIG. 5A, for the return light pulse A detected duringdetection period B, the most recently emitted light pulse is pulse Bwhich corresponds to the detection period B during which the returnlight pulse A was detected. As such, the computing system generates aclose range hypothesis to determine whether or not the detected returnlight pulses reflected off a nearby object positioned within the nominaldetection range of the LIDAR device. In this example, the computingsystem, e.g., part of or coupled to device 200, generates a close rangehypothesis that the detected light pulse A was emitted at the time lightpulse B was emitted, reflected off an object positioned within the LIDARdevices' nominal detection range, and therefore returned withindetection period B as it did.

Further, when generating an alternate range hypothesis, the alternaterange hypothesis could be a far range hypothesis or could be a“proximate” range hypothesis.

Specifically, the computing system may generate a far range hypothesisthat the detected return light pulses reflected off a distant objectpositioned beyond the maximum unambiguous detection range of the LIDARdevice. When generating a far range hypothesis, the computing system maydetermine a range respectively for each detected return light pulseaccording to a time delay relative to an emission time of a previouslyemitted light pulse. In one case, for a given return light pulsedetected during a given detection period having a corresponding emittedlight pulse, the previously emitted light pulse may be one thatimmediately precedes in time the emitted light pulse corresponding tothe given detection period. In other cases, however, the previouslyemitted light pulse may be a two times previous light pulse or a threetimes previous light pulse, and so on.

The computing system may generate a proximate range hypothesis that thedetected return light pulses reflected off a proximate object positionedcloser than the minimum detection range of the LIDAR device. Forexample, consider an embodiment in which at time t0, a light pulse P0 isemitted, and at a time t1, the LIDAR begins to watch for reflections ofP0's light. Further, at at time t2, a light pulse P1 is emitted, whilethe LIDAR continues to watching for reflections of P0's light. Then, ata time t3, the LIDAR stops watching for reflections of P0's light, andbegins to watch for reflections of P1's light. In this example, if anunexpected object is located closer than the minimum detection range ofthe LIDAR device, it may reflect back P1's light before t3. In one anembodiment, the computing system may generate a proximate rangehypothesis that determines the range of the object that reflected P1'slight based on the emission time of P1, even though the reflection wasreceived during the period in which the LIDAR was watching forreflections of P0, e.g., because the system is aware that there is anoffset before detection periods begin and an overlap between detectionperiods and emissions. Accordingly, when generating a proximate rangehypothesis, the computing system may determine a range respectively foreach detected return light pulse according to a time delay relative toan emission time of a subsequently emitted light pulse. Thissubsequently emitted light pulse may be an emitted light pulse thatcorresponds to a detection period following the one during which a givenlight pulse was detected.

As such, for instance, the computing system may determine (i) a firstset of ranges in accordance with a time delay relative to correspondingemission times of a plurality of first emitted light pulses and (ii) asecond set of ranges in accordance with a time delay relative tocorresponding emission times of a plurality of second emitted lightpulses. The first set of ranges may correspond to a close rangehypotheses and the second set ranges may correspond to an alternaterange hypothesis. Alternatively, the first set may correspond to analternate range hypotheses and the second set may correspond to a closerange hypothesis, or the first set may correspond to a first alternaterange hypotheses and the second set may correspond to a second alternaterange hypothesis. Other combinations of range hypotheses are possible aswell. In any case, the first and second emitted pulses may be differentfrom one another, as at least one of the second emitted pulses would bedifferent from each of the plurality of first emitted pulses.

At block 608, method 600 involves selecting between using the first setof ranges as a basis for object detection and using the second set ofranges as a basis for object detection. And at block 610, method 600involves engaging in object detection in accordance with the selecting.

Once the computing system generates two or more range hypotheses for thedetected return light pulses, the computing system may then determinewhich one of these range hypotheses is correct and thus which rangesshould be used as a basis for object detection. In accordance with thepresent disclosure, the computing system could do so based on comparisonto known object(s) and/or based on consideration of similarity of rangesin a given hypothesis, among other possibilities.

In one example, the computing system may determine that the first set ofranges closely resembles a known object and/or that the second set ofranges does not resemble any known objects, and the system mayresponsively select the first set of ranges to be used as basis forobject detection. Alternatively, the computing system may determine thatthe second set of ranges closely resembles a known object and/or thatthe first set of ranges does not resemble any known objects, and thesystem may responsively select the second set of ranges to be used asbasis for object detection.

In this example, the computing system could determine whether or not aset of ranges is representative of one or more known objects, such asbased on object recognition techniques. For instance, the computingsystem could have stored on or otherwise have access to a plurality ofpoint clouds each respectively indicative of a known object (e.g., roadsign(s)). Therefore, the computing system could assemble a point cloudbased on a particular set of ranges, and could then determine whether ornot this assembled point cloud matches at least one of the plurality ofpoint clouds. If the assembled point cloud substantially matches atleast one of the plurality of point clouds, then the computing systemmay determine that the particular set of ranges is representative of atleast one known object. Otherwise, the computing system may determinethat the particular set of ranges is not representative of at least oneknown object.

In another example, the computing system may determine that the firstset includes ranges that are substantially similar to one another and/orthat the second set includes ranges that are substantially differentfrom one another, and the system may responsively select the first setof ranges to be used as basis for object detection. Alternatively, thecomputing system may determine that the second set includes ranges thatare substantially similar to one another and/or that the first setincludes ranges that are substantially different from one another, andthe system may responsively select the second set of ranges to be usedas basis for object detection.

In this example, the computing system could determine whether or notranges in a set are substantially similar to one another. For instance,if the computing system determines that ranges of a set substantiallymatch one another (e.g., within a threshold tolerance), then thecomputing system may responsively determine that ranges of the set aresubstantially similar to one another. Otherwise, the computing systemmay responsively determine that ranges of the set are not substantiallysimilar to one another. In another instance, the computing system maydetermine whether or not a difference between the smallest range in theset and the greatest range in the set exceeds a threshold difference(e.g., established via additional engineering input). If the computingsystem determines that this difference exceeds the threshold difference,then then computing system may responsively determine that ranges of theset are not substantially similar to one another. But if the computingsystem determines that this difference does not exceeds the thresholddifference, then the computing system may responsively determine thatranges of the set are substantially similar to one another. Otherinstances and examples are also possible.

In a situation in which the return light pulses are detected duringcorresponding detection periods for each of the plurality of firstemitted light pulses and thus in which the first set corresponds to aclose range hypothesis, the set of ranges that the computing system endsup selecting may indicate whether the detected return light pulsesreflected off nearby object(s) or whether the detected return lightpulses reflected off distant and/or proximate object(s) positionedoutside the nominal detection range of the LIDAR device.

In particular, if the computing system selects use of the first set ofranges as a basis for object detection, then the detected return lightpulses are light pulses that reflected off one or more nearby objectspositioned within the nominal detection range of the LIDAR device. Butif the computing system selects use of the second set of ranges as abasis for object detection, then the detected return light pulses arelight pulses that reflected off one or more objects positioned outsidethe nominal detection range of the LIDAR device. Other examplesituations are also possible.

In one embodiment, after the computing system selects a set of ranges touse as a basis for object detection, the computing system may thenengage in object detection accordingly. Generally, engaging in objectdetection could involve detecting presence of an object, determining adistance of the object away from the LIDAR device, and/or identifyingthe object, among other possibilities.

In particular, if the computing system determines that the first set ofranges should be used as a basis for object detection, the computingsystem may responsively use the first set of ranges rather than thesecond set of ranges as basis for object detection. For instance, thecomputing system may determine based on the first set of ranges that anobject is positioned at a certain range away from the LIDAR device. Thecomputing system could determine this certain range to be one of theranges of the first set or could determine this certain range to be anaverage of the ranges of the first set, among other possibilities.Additionally or alternatively, the computing system could assemble apoint cloud based on the first set of ranges and could use this pointcloud as basis for identifying the object in accordance with objectrecognition technique(s).

However, if the computing system determines that the second set ofranges should be used as a basis for object detection, the computingsystem may responsively use the second set of ranges rather than thefirst set of ranges as basis for object detection. For instance, thecomputing system may determine based on the second set of ranges that anobject is positioned at a certain range away from the LIDAR device. Thecomputing system could determine this certain range to be one of theranges of the second set or could determine this certain range to be anaverage of the ranges of the second set, among other possibilities.Additionally or alternatively, the computing system could assemble apoint cloud based on the second set of ranges and could use this pointcloud as basis for identifying the object in accordance with objectrecognition technique(s). Other instances are also possible.

Given this implementation, the computing system could determine theappropriate ranges to use for basis for object detection, even when oneor more detected return light pulses are light pulses that reflect offproximate and/or distant object(s) and are received before or afterdetections period associated with their emitted light pulses began orended.

FIGS. 7A to 7B next illustrate how multiple range hypotheses andapplication of dither can together help a computing system select rangesto use as a basis for object detection.

In particular, FIG. 7A shows light pulses A-F emitted respectively atemission times A-F in accordance with an emission time sequence #2 thatincludes application of dither. These emission times establish detectionperiods A-F of various durations. In line with FIGS. 5A-5B, light pulsesA-F each reflect off the distant object 404 and, as a result, are eachrespectively detected during a subsequent detection period.

In this case, however, when the computing system determines candidateranges associated with detected light pulses A-F in accordance with aclose range hypothesis, the ranges may be substantially different fromone another due to the application of dither. For instance, thecomputing system may determine that the LIDAR device 200 detected lightpulse A at a detection time Tn0 of 83 ns relative to emission time B,which corresponds to a range of 12.5 m as shown in FIG. 7B. But thecomputing system may determine that the LIDAR device 200 detected lightpulse B at a detection time Tn1 of 183 ns relative to emission time C,which corresponds to a range of 27.5 m as shown in FIG. 7B. And as shownin FIG. 7A-7B, a similar approach may be used for determining rangesrespectively with regards to detection time Tn2, Tn3, Tn4, and Tn5.

Given this, as shown in FIG. 7B, the computing system determines a closerange hypothesis including ranges 702 that are substantially differentfrom one another and, as a result, could determine that these ranges 702should not be used as basis for object detection. The determination tonot use ranges 702 would be correct, as light pulses A-F in factreflected off the distant object 404 that is positioned beyond themaximum unambiguous detection range of the LIDAR device 200. Thus,avoiding use of the close range hypothesis for object detection couldhelp avoid a false detection of a nearby object.

Moreover, the computing system could additionally determine candidateranges associated with detected light pulses A-F in accordance with afar range hypothesis. For instance, the computing system may determinethat the LIDAR device 200 detected light pulse A at a detection time Tf0of 533 ns relative to emission time A, which corresponds to a range of80 m as shown in FIG. 7B. And as indicated by detection times Tf1 toTf5, a similar approach could be used for determining ranges associatedwith light pulses B-F, thereby resulting in second ranges 704corresponding to a far range hypothesis of an object being positioned at80 m away from the LIDAR device 200.

Given this, as shown in FIG. 7B, the computing system determines a farrange hypothesis including ranges 704 that are substantially similar toone another and, as a result, could determine that these ranges 704should be used as basis for object detection. This far range hypothesisis accurate, as light pulses A-F in fact reflected off the distantobject 404 that is positioned beyond the maximum unambiguous detectionrange of the LIDAR device 200. Therefore, the computing systemdetermines the appropriate ranges to use as a basis for objectdetection. Other illustrations are also possible.

VI. ADDITIONAL APPLICATIONS AND CONSIDERATIONS

a. Range Ambiguity Involving Multiple Detections in the Same DetectionPeriod

In practice, a computing system could encounter range ambiguity insituations other than those described above, such as when the LIDARdevice detects multiple return light pulses respectively during one ormore detection periods.

More specifically, when a LIDAR device detects a light pulse thatreflected off an object positioned outside the nominal detection range,the LIDAR device may detect this light pulse at a detection time afterthe end of a detection period that corresponds to that light pulse or ata detection time before start of a detection period that corresponds tothat light pulse, which may lead to range ambiguity in the context ofmultiple light pulse detection in the same detection period.

For instance, referring again to FIG. 4C, the LIDAR device 200 maydetect the light pulse emitted at emission time 406A during a detectionperiod that corresponds to another light pulse emitted at emission time406B and therefore during a detection period that follows detectionperiod 408. This scenario could lead to the computing system determiningthat the LIDAR device detected multiple return light pulses during thesame detection period, and thus the computing system determining twopossible time delays relative to an emitted light pulse that correspondsto this detection period. Consequently, this scenario may lead toambiguity as it may be unclear which of these return light pulsescorresponds to the detection period and thus which of these return lightpulses to use as basis for determining a distance to an object.

By way of example, FIGS. 8A-8B illustrate how a LIDAR device coulddetect multiple return light pulses during the same detection period andhow such detection of multiple return light pulses during the samedetection period may lead to ambiguity. In particular, FIG. 8A showslight pulses A-G emitted respectively at emission times A-G inaccordance with a periodic emission time sequence #3. In line with thediscussion above, these periodic emission times establish detectionperiods A-G each of the same 400 ns duration. As shown, light pulses A,C, E, and G reflect off the nearby object 402 and are thus respectivelydetected by the LIDAR device 200 in their corresponding detectionperiods A, C, E, and G. However, light pulses B, D, and F reflect offthe distant object 404 and, as a result, are each respectively detectedduring a subsequent detection period.

Consequently, the LIDAR device 200 ambiguously detects multiple returnlight pulses respectively during each such subsequent detection period.For instance, light pulse B is detected by the LIDAR device 200 duringdetection period C, which is established for detection of light pulse Crather than for detection of light pulse B. In this regard, the LIDARdevice 200 detects light pulse B at a detection time B of 133 nsrelative to emission time C, which corresponds to a range of 20 m, andalso detects light pulse C at a detection time C of 350 ns relative toemission time C, which corresponds to a range of 52.5 m. A similarsituation is encountered with regards to detection of light pulses D andE during detection period E as well as with regards to detection oflight pulses F and G during detection period G.

As such, the computing system could generate a close range hypothesisbased on detection of light pulses A, C, E, and G, which includes ranges802 each having a value of 52.5 m. Additionally, the computing systemmay generate a close range hypothesis based on detection of light pulsesB, D, and F, which includes ranges 804 each having a value of 20 m. Andgiven these possible sets of ranges 802 and 804, the computing systemoperating LIDAR device 200 may be unable to determine with certaintywhether an object is positioned at 52.5 m away from the LIDAR device 200and/or whether an object is positioned at 20 m away from the LIDARdevice 200, thereby leading to range ambiguity. Other illustrations arealso possible.

To help resolve the issue of range ambiguity, a time-varying dither canbe applied to the emission time sequence. In practice, as noted,application of dither may involve pseudo-random deviation of a periodicsignal away from periodicity, such as by application of noise to thesignal, among other possibilities. In this regard, the computing systemmay apply pseudo-random dither to respective emission timing of some,but not all, emitted light pulses, so as to respectively shift each suchrespective emission timing away from periodicity by a pseudo-randomduration. With this implementation, the LIDAR device could stillpossibly detect multiple return light pulses respectively during each ofa plurality of detection periods. But due to the shifts in periodicity,the computing system could potentially determine which one of thesereturn light pulses corresponds to the respective detection period andwhich one does not correspond to the respective detection period.

More specifically, for each respective detection period that begins at arespective emission time, the computing system could determine a firstrange associated with a first return light pulse according to a timedelay relative to the respective emission time and could determine asecond range associated with a second return light pulse also accordingto a time delay relative to the respective emission time. Once thecomputing system determines the first set of first ranges and the secondset of second ranges, one of these sets is less likely than the other toresemble a recognizable object due to the above-mentioned shifts, whichcould help the computing system determine which ranges to use forpurposes of object detection. For instance, if the second return lightpulses are those that reflected off the distant object, then the secondset is less likely than the first set to resemble a recognizable object.Therefore, the computing system could determine that ranges of thesecond set are randomly scattered and thus responsively determine thatranges of the first set should be used for purposes of object detection.

FIGS. 9A-9B next illustrate how application of dither could help resolverange ambiguity. In particular, FIG. 9A shows light pulses emittedrespectively at emission times A-G in accordance with a non-periodicemission time sequence #4 that includes application of dither. In linewith the discussion above, these periodic emission times establishdetection periods A-G, some of which are of the same duration and someof which are of different durations. As with emission time sequence #3,light pulses A, C, E, and G reflect off the nearby object 402 and, as aresult, are each respectively detected by the LIDAR device 200 in theircorresponding detection periods A, C, E, and G. Also, as with emissiontime sequence #3, light pulses B, D, and F reflect off the distantobject 404 and, as a result, are each respectively detected during asubsequent detection period. In this case, however, due application ofdither, the computing system could potentially disambiguate betweenmultiple return light pulses detected during the same detection period.

More specifically, FIGS. 9A-9B show that the range corresponding todetection of light pulses A, C, E, and G is at 52.5 m away from theLIDAR device 200. But FIGS. 9A-9B also show that, due to application ofdither, the ranges corresponding to light pulses B, D, and F aresubstantially different from one another. Namely, the LIDAR device 200detected light pulse B at a detection time B of 183 ns relative toemission time C, which corresponds to a range of 27.5 m, detected lightpulse D at a detection time D of 158 ns relative to emission time E,which corresponds to a range of 23 m, and detected light pulse F at adetection time F of 133 ns relative to emission time G, whichcorresponds to a range of 20 m. In this way, the computing systemdetermines a first set of ranges 902 that are the same or similar to oneanother, as well as a second set of ranges 904 that are substantiallydifferent from one another. As such, the computing system coulddetermine that ranges 904 are randomly scattered and thus responsivelydetermine that ranges 902 should be used for purposes of objectdetection. Other illustrations are possible as well.

Although the approach of this embodiment can help overcome rangeambiguity, there may be certain deficiencies. For example, when thecomputing system determines two or more possible sets of ranges in linewith the discussion above, in some cases, each such set of ranges couldresemble a recognizable object. In such cases, the computing system maynot be able to determine with a high level of certainty which of thesesets of ranges to use for purposes of object detection. Moreover,whether or not the computing system is able to disambiguate betweenmultiple return light pulses with a high level of certainty, theexisting implementation does not provide for detection of an objectpositioned outside the nominal detection range, such as of a distantobject that reflects light pulses and causes the range ambiguity.

b. Using an Alternate Range Hypothesis to Detect a Distant Object

FIG. 10 is a flowchart illustrating a method 1000, according to anexample implementation. In particular, method 1000 may be implemented togenerate an alternate range hypothesis and then use that alternate rangehypothesis to detect an object positioned outside the nominal detectionrange of a LIDAR device. Although method 1000 is generally described inthe context of generating a far range hypothesis, it should beunderstood that method 1000 may additionally or alternatively apply inthe context of generating a proximate range hypothesis.

At block 1002, method 1000 involves operating a LIDAR device to emitlight pulses at emission times in accordance with an emission timesequence, where the emission time sequence includes a time-varyingdither, and to detect return light pulses in accordance with a detectiontime sequence, where the detection time sequence includes, for eachemitted light pulse, a corresponding detection period for detection of acorresponding return light pulse, and where a detection time of a returnlight pulse relative to a corresponding emission time of a correspondingemitted light pulse is indicative of a range to an object that reflectedthe corresponding emitted light pulse.

In line with the discussion above, a computing system could operate aLIDAR device to emit and detect light pulses in accordance with certaintiming. For instance, the computing system could operate the LIDARdevice to emit light pulses in accordance with an emission time sequenceincluding a time-varying dither. As discussed, the emission timesequence may help establish a detection time sequence according to whichthe LIDAR device detects return light pulses. Generally, this detectiontime sequence may include a corresponding detection period respectivelyfor each emitted light.

In particular, a corresponding detection period for a given light pulsemay begin immediately following or at some time after emission of thatgiven light pulse, and may end before or after emission a subsequentlight pulse. During this corresponding detection period, the LIDARdevice could detect a given return light pulse that corresponds to thegiven emitted light pulse, such as when the given emitted light pulsereflects off an object to result in that return light pulse. After theLIDAR device detects the given return light pulse at a certain detectiontime, the computing system could then determine a range to an objectthat reflected the given emitted light pulse. As discussed, thecomputing system could determine this range according to a time delaybetween the detection time of the given return light pulse and theemission time of the given emitted light pulse.

At block 1004, method 1000 involves determining that the LIDAR devicedetected a set of multiple return light pulses during correspondingdetection periods for each of a plurality of first emitted light pulses,where each set of multiple return light pulses includes at least arespective first return light pulse and a respective second return lightpulse.

In line with the discussion above, a computing system could determinethat the LIDAR device detected multiple return light pulses respectivelyduring two or more detection periods. For instance, a plurality of firstemitted light pulses could each respectively have a correspondingdetection period. But due to reflection of one or more light pulses offproximate and/or distant object(s), the LIDAR device could instead endup detecting multiple return light pulses respectively during each suchcorresponding detection. As such, for each such corresponding detectionperiod, the computing system could determine that the LIDAR devicedetected at least a respective first return light pulse as well as arespective second return light pulse. Moreover, in each correspondingdetection period, one of these return light pulses may be a pulse thatreflected off an object positioned outside the nominal detection rangeof the LIDAR device, and the other one of these return light pulses maybe a pulse that reflected off an object positioned within the nominaldetection range that is thus associated with the detection period atissue. Other scenarios are possible as well.

At block 1006, method 1000 involves making a determination that thefirst return light pulses correspond to the plurality of first emittedlight pulses and that the second return light pulses potentiallycorrespond to a plurality of second emitted light pulses.

In accordance with the present disclosure, once the computing systemdetermines that the LIDAR device detected multiple return light pulsesrespectively during two or more detection periods, the computing systemmay determine which of these return light pulses correspond to theplurality of first emitted light pulses. Namely, the computing systemmay determine which of these return light pulses reflected off object(s)within the nominal detection range. In some embodiments, the computingsystem could do so by using any of the above-described implementationsfor resolving range ambiguity and/or could do so in accordance with theapproach for resolving range ambiguity described herein in associationwith method 1200, among other options. In any case, for sake ofsimplicity, an assumption could be made that the computing systemdetermined that the above-mentioned first return light pulses correspondto the plurality of first emitted light pulses, and thus that the rangescorresponding to these first return light pulses should be used forpurposes of object detection.

After or while determining that the first return light pulses correspondto the plurality of first emitted light pulses, the computing system maydetermine that the above-mentioned second return light pulsespotentially correspond to a plurality of second emitted light pulses. Inparticular, rather than disregarding or discarding detection of thesecond return light pulses after disambiguating between the multiplereturn light pulses, the computing system may select a plurality ofsecond emitted light pulses to which the second return light pulsescould potentially correspond. For instance, for each second return lightpulse, the computing system could respectively select a previouslyemitted light pulse, which may be a light pulse that corresponds to adetection period that precedes (e.g., immediately precedes) the oneduring which the second return light pulse was actually detected. As aresult, at least one of the second emitted light pulses that is used tocalculate a range for a return light pulse could be different from eachof the plurality of first emitted light pulses.

By way of example, referring again to FIG. 8A, return light pulses A, C,E, and G are respectively detected at their corresponding detectionperiods and could therefore be considered to be the first return lightpulses that correspond to the plurality of first emitted light pulses.As a result, return light pulses B, D, and F could therefore beconsidered to be the second return light pulses that reflected off adistant object and thus were detected during a subsequent detectionperiod in line with the discussion above.

In this example, for each of return light pulses B, D, and F, thecomputing system could respectively select a previously emitted lightpulse, which may corresponds to a detection period that precedes the oneduring which the return light pulse was actually detected. For instance,the computing system could select emitted light pulses B, D, and F,which respectively correspond to detection periods B, D, and F. Asshown, detection periods B, D, and F are those that actually correspondto light pulses B, D, and F. Other examples are possible as well.

At block 1008, method 1000 involves, in response to making thedetermination, determining that the second return light pulses havedetection times relative to corresponding emission times of theplurality of second emitted light pulses that are indicative of aparticular set of ranges.

Once the computing system selects or otherwise determines the pluralityof second emitted light pulses that potentially correspond to thedetected second return light pulses, the computing system couldresponsively generate a far range hypothesis for the second return lightpulses. Specifically, for each second return light pulse, the computingsystem could respectively determine an associated range according to atime delay relative to an emission time of one of the plurality ofsecond emitted light pulses, which may be an emitted light pulsecorresponding to a detection period that precedes the one during whichthe second return light pulse was detected. In this way, the computingsystem may determine associated ranges to result in a particular set ofranges that is considered to be one possible alternate range hypothesisfor the second return light pulses.

By way of example, FIGS. 11A-11B illustrate determination of a far rangehypothesis. In particular, FIG. 11A shows the emission time sequence #4introduced in FIG. 9A. But in this case, assuming again that returnlight pulses B, D, and F are considered to be the second return lightpulses, the computing system respectively determines rangescorresponding to these light pulses according to a time delay relativeto an emission time of a previously emitted light pulse. Namely, asshown in FIG. 11A, the computing system determines that return lightpulses B has a detection time of 533 ns relative to emission time B,that return light pulses D has a detection time of 533 ns relative toemission time D, and that return light pulses F has a detection time of533 ns relative to emission time F. And as shown in FIG. 11B, thesedetection times of return light pulses B, D, F each have a correspondingrange of 80 m. Therefore, these corresponding ranges result in aparticular set of ranges 1100 considered to be a far range hypothesis.Other examples are also possible.

At block 1010, method 1000 involves making a further determination ofwhether or not to use the particular set of ranges as a basis for objectdetection. At block 1012, method 1000 involves engaging in objectdetection in accordance with the further determination.

As noted above, the computing system could use an alternate rangehypothesis as basis to detect an object positioned outside a nominaldetection range of a LIDAR device. In particular, once the computingsystem determines the particular set of ranges considered to be analternate range hypothesis for the second return light pulses, thecomputing system could determine whether or not the particular set ofrange should be used as a basis for object detection. The computingsystem could do so in various ways.

In one example, the computing system could determine whether or not theparticular set of ranges is representative of one or more known objects.As noted, the computing system could do so based on object recognitiontechniques. In this example, if the computing system determines that theparticular set of ranges is representative of one or more known objects,the computing system may responsively determine that the particular setof ranges should be used as a basis for further object detection. Forinstance, in line with the discussion above, the computing system couldassemble a point cloud based on the particular set of ranges, and couldthen determine that this assembled point cloud matches at least one ofthe plurality of point clouds stored by the computing system. Inresponse to determining this match, the computing system could then usethe assembled point cloud as basis for identifying the distant objectand/or could establish a certain range at which the object representedby the assembled point cloud is positioned (e.g., the certain rangecould be established to be an average of the ranges of the particularset), among other options. However, if the computing system determinesthat the particular set of ranges is not representative of at least oneknown object, the computing system may responsively determine that theparticular set of range should not be used as a basis for further objectdetection.

In another example, the computing system may determine whether or notranges of the particular set are substantially similar to one another.In this example, if the computing system determines that ranges of theparticular set are substantially similar to one another, the computingsystem may responsively determine that the particular set of rangeshould be used as a basis for object detection. However, if thecomputing system determines that ranges of the particular set are notsubstantially similar to one another, the computing system mayresponsively determine that the particular set of ranges should not beused as a basis for object detection.

In accordance with the present disclosure, if the computing systemdetermines that the particular set of range should not be used as abasis for object detection, the computing system may not use theparticular set of ranges as basis for object detection. For instance,the computing system could discard or disregard signals as noise or theranges of the particular set as unreliable, among other options.

However, if the computing system determines that the particular set ofrange should be used as a basis for object detection, the computingsystem may then engage in object detection accordingly. Generally,engaging in object detection could involve detecting presence of anobject, determining a distance of the object away from the LIDAR device,and/or identifying the object, among other possibilities.

For instance, the computing system may determine based on the particularset of ranges that a distant object is positioned at a certain rangeaway from the LIDAR device. The computing system could determine thiscertain range to be one of the ranges of the particular set or coulddetermine this certain range to be an average of the ranges of theparticular set, among other possibilities. Additionally oralternatively, if the computing system has not already done so as partof the process of determining whether or not the particular set of rangeshould be used as a basis for object detection, the computing systemcould assemble a point cloud based on the particular set of ranges. Andthe computing system could use this point cloud as basis for identifyingthe distant object in accordance with object recognition technique(s).Other examples are possible as well.

In this way, an alternate range hypothesis could help provide additionalinformation indicative of an object being positioned outside the nominaldetection range of a LIDAR device. Such additional information could beused by the computing system to optimize navigation decisions for avehicle that operates in an autonomous mode, among other outcomes.

FIGS. 11A-11B further illustrate how an alternate range hypothesis couldhelp with detection of object(s) positioned outside the nominaldetection range of a LIDAR device. As noted above, the particular set ofranges 1100 is considered to be a far range hypothesis. Thus, based on adetermination that ranges of the particular set of ranges 1100 are equalor substantially similar to one another, the computing system coulddetermine that ranges of the particular set of ranges 1100 should beused as basis for object detection. Accordingly, as shown, the computingsystem could determine that a distant object is positioned at about 80 maway from the LIDAR device 200, which is an accurate determination asobject 404 is in fact shown in FIG. 4A to be positioned at 80 m awayfrom the LIDAR device 200. Other illustrations are also possible.

In a further aspect, when a LIDAR device is positioned on a vehicle, acomputing system could use the vehicle's speed as an additional factorfor evaluating a range hypothesis. In particular, when a vehicle movestowards an object and a LIDAR device detects return light pulsesreflected off that object, the detection time of those return pulsestends to get shorter over time as the vehicle approaches the object, andthus ranges determined based on these detection times may decrease asthe vehicle approaches the object. In practice, such decrease indetermined range over time may be predictable based on the vehicle'sspeed. Thus, when the computing system generates a range hypothesisbased on the detection times of such pulses, the computing system coulddetermine whether or not ranges of the hypothesis decrease over time aswould be expected based on the vehicle's speed. If so, then thecomputing system may responsively determine that the range hypothesis iscorrect. Otherwise, the computing system may responsively determine thatthe range hypothesis is incorrect. Other aspects are possible as well.

c. Using an Alternate Range Hypothesis to Disambiguate Between MultipleReturn Light Pulses Respectively Detected During a Plurality ofDetection Periods

FIG. 12 is a flowchart illustrating a method 1200, according to anexample implementation. In particular, method 1200 may be implemented togenerate an alternate range hypothesis and then use that alternate rangehypothesis to disambiguate with a higher level of certainty betweenmultiple return light pulses respectively detected during a plurality ofdetection periods. Although method 1200 is generally described in thecontext of generating a far range hypothesis, it should be understoodthat method 1200 may additionally or alternatively apply in the contextof generating a proximate range hypothesis.

At block 1202, method 1200 involves operating a LIDAR device to emitlight pulses at emission times in accordance with an emission timesequence, where the emission time sequence includes a time-varyingdither, and to detect return light pulses in accordance with a detectiontime sequence, where the detection time sequence includes, for eachemitted light pulse, a corresponding detection period for detection of acorresponding return light pulse, and where a detection time of a returnlight pulse relative to a corresponding emission time of a correspondingemitted light pulse is indicative of a range to an object that reflectedthe corresponding emitted light pulse.

As noted above, a computing system could operate a LIDAR device to emitand detect light pulses in accordance with certain timing. For instance,the computing system could operate the LIDAR device to emit light pulsesin accordance with an emission time sequence including a time-varyingdither. As discussed, the emission time sequence may help establish adetection time sequence according to which the LIDAR device detectsreturn light pulses. Generally, this detection time sequence may includea corresponding detection period respectively for each emitted lightpulse.

In particular, a corresponding detection period for a given light pulsemay begin immediately following or at some time after emission of thatgiven light pulse, and may end before or after emission a subsequentlight pulse. During this corresponding detection period, the LIDARdevice could detect a given return light pulse that corresponds to thegiven emitted light pulse, such as when the given emitted light pulsereflects off an object to result in that return light pulse. After theLIDAR device detects the given return light pulse at a certain detectiontime, the computing system could then determine a range to an objectthat reflected the given emitted light pulse. The computing system coulddetermine this range according to a time delay between the detectiontime of the given return light pulse and the emission time of the givenemitted light pulse.

At block 1204, method 1200 involves determining that the LIDAR devicedetected a set of multiple return light pulses during correspondingdetection periods for each of a plurality of first emitted light pulses,where each set of multiple return light pulses includes at least arespective first return light pulse and a respective second return lightpulse.

As noted above, a computing system could determine that the LIDAR devicedetected multiple return light pulses respectively during one or moredetection periods. For instance, a plurality of first emitted lightpulses could each respectively have a corresponding detection period.But due to reflection of one or more light pulses off object(s)positioned outside the nominal detection range, the LIDAR device couldinstead end up detecting multiple return light pulses respectivelyduring each such corresponding detection. As such, for each suchcorresponding detection period, the computing system could determinethat the LIDAR device detected at least a respective first return lightpulse as well as a respective second return light pulse. Moreover, ineach corresponding detection period, one of these return light pulses isa pulse that reflected off an object positioned outside the nominaldetection range of the LIDAR device, and the other one of these returnlight pulses is a pulse that reflected off an object positioned withinthe nominal detection range that is thus associated with the detectionperiod at issue. Other scenarios are possible as well.

At block 1206, method 1200 involves determining that (i) the firstreturn light pulses have detection times relative to correspondingemission times of the plurality of first emitted light pulses that areindicative of a first set of ranges, (ii) the second return light pulseshave detection times relative to corresponding emission times of theplurality of first emitted light pulses that are indicative of a secondset of ranges, and (iii) the second return light pulses have detectiontimes relative to corresponding emission times of a plurality of secondemitted light pulses that are indicative of a third set of ranges.

In line with the discussion above, when the computing system determinesthat the LIDAR device detected multiple return light pulses respectivelyduring a plurality of detection periods, the computing system maydetermine, respectively for each detected return light pulse, acorresponding range according to a time delay relative to a mostrecently emitted light pulse.

For instance, as noted, the plurality of first emitted light pulsescould each respectively have a corresponding detection period and, foreach such corresponding detection period, the computing system coulddetermine that the LIDAR device detected at least a respective firstreturn light pulse as well as a respective second return light pulse.For each respective first return light pulse, the computing system couldthen determine a corresponding first range according to a time delayrelative to emission time of the first emitted light corresponding tothe detection period during which the respective first return lightpulse was detected. Additionally, for each respective second returnlight pulse, the computing system could then determine a correspondingsecond range according to a time delay relative to emission time of thefirst emitted light corresponding to the detection period during whichthe respective second return light pulse was detected. In this way, thedetermined first ranges result in a first set of ranges and thedetermined second ranges result in a second set of ranges.

Further in line with the discussion above, when the computing systemdetermines such first and second sets of ranges, these sets may giverise to range ambiguity, as it may be unclear which of these sets shouldbe used for purposes of object detection. Although the above-mentionedexisting implementation could sometimes help overcome this rangeambiguity, in accordance with the present disclosure, a computing systemfurther could generate an alternate range hypothesis, to further assistin disambiguating the range ambiguity between by the first and secondsets of ranges.

More specifically, the computing system may select a plurality of secondemitted light pulses to which the second return light pulses couldpotentially correspond. For example, for each second return light pulse,the computing system could respectively select a previously emittedlight pulse, which may be a light pulse that corresponds to a detectionperiod that precedes (e.g., immediately precedes) the one during whichthe second return light pulse was actually detected. As a result, atleast one of the second emitted light pulses that is used to calculate arange for a return light pulse could be different from each of theplurality of first emitted light pulses.

Once the computing system selects or otherwise determines the pluralityof second emitted light pulses that potentially correspond to thedetected second return light pulses, the computing system couldresponsively generate an alternate range hypothesis for the secondreturn light pulses. Specifically, for each second return light pulse,the computing system could respectively determine an associated rangeaccording to a time delay relative to an emission time of one of theplurality of second emitted light pulses, which may be an emitted lightpulse corresponding to a detection period that precedes the one duringwhich the second return light pulse was detected. In this way, thecomputing system may determine associated ranges to result in a thirdset of ranges that is considered to be one possible alternate rangehypothesis for the second return light pulses. Moreover, if thisalternate range hypothesis is a far range hypothesis, the ranges of thethird set may be greater than ranges of the above-mentioned second set,despite both sets of ranges being associated with the second returnlight pulses.

At block 1208, method 1200 involves, based on the third set of ranges,selecting between using the first set of ranges as a basis for objectdetection and using the second set of ranges as a basis for objectdetection. And at block 1210, method 1200 involves engaging in objectdetection in accordance with the selecting.

More specifically, in accordance with the present disclosure, thecomputing system may use the generated alternate range hypothesis tohelp overcome range ambiguity, and the computing system could do so invarious ways.

In one example, the computing system could determine whether or not thethird set of ranges is representative of one or more known objects, andcould do so as discussed above, for instance.

In this example, if the computing system determines that the third setof ranges is representative of one or more known objects, then thecomputing system could responsively determine that the generatedalternate range hypothesis for the second return light pulses is likelycorrect. Based on a determination that the generated alternate rangehypothesis for the second return light pulses is likely correct, thecomputing system may determine that the close range hypothesis for thesecond return light pulses, which includes the second set of ranges, islikely incorrect. Therefore, in response to determining that the thirdset of ranges is representative of one or more known objects, thecomputing system may determine that the computing system should use, forpurposes of object detection, the first set of ranges associated withthe first return light pulses rather than the second set of rangesassociated with the second return light pulses.

In contrast, if the computing system determines that the third set ofranges is not representative of any known object, then the computingsystem could responsively determine that the generated alternate rangehypothesis for the second return light pulses is likely incorrect. Basedon a determination that the generated alternate range hypothesis for thesecond return light pulses is likely incorrect, the computing system maydetermine that the close range hypothesis for the second return lightpulses, which includes the second set of ranges, is likely correct.Therefore, in response to determining that the third set of ranges isnot representative of any known object, the computing system maydetermine that the computing system should use, for purposes of objectdetection, the second set of ranges associated with the second returnlight pulses rather than the first set of ranges associated with thefirst return light pulses.

In another example, the computing system may determine whether or notranges of the third set are substantially similar to one another, andcould do so as discussed above, for instance.

In this example, if the computing system determines that the third setof ranges are substantially similar to one another, then the computingsystem could responsively determine that the generated alternate rangehypothesis for the second return light pulses is likely correct. Basedon a determination that the generated alternate range hypothesis for thesecond return light pulses is likely correct, the computing system maydetermine that the close range hypothesis for the second return lightpulses, which includes the second set of ranges, is likely incorrect.Therefore, in response to determining that the third set of ranges aresubstantially similar to one another, the computing system may determinethat the computing system should use, for purposes of object detection,the first set of ranges associated with the first return light pulsesrather than the second set of ranges associated with the second returnlight pulses.

In contrast, if the computing system determines that the third set ofranges are not substantially similar to one another, then the computingsystem could responsively determine that the generated alternate rangehypothesis is likely incorrect. Based on a determination that thegenerated alternate range hypothesis for the second return light pulsesis likely incorrect, the computing system may determine that the closerange hypothesis for the second return light pulses, which includes thesecond set of ranges, is likely correct. Therefore, in response todetermining that the third set are not substantially similar to oneanother, the computing system may determine that the computing systemshould use, for purposes of object detection, the second set of rangesassociated with the second return light pulses rather than the first setof ranges associated with the first return light pulses. Other examplesare also possible.

In accordance with the present disclosure, if the computing systemdetermines that the first set of ranges should be used as a basis forobject detection, the computing system may responsively use the firstset of ranges rather than the second set of ranges as basis for objectdetection. For instance, the computing system may determine based on thefirst set of ranges that a nearby object is positioned at a certainrange away from the LIDAR device. The computing system could determinethis certain range to be one of the ranges of the first set or coulddetermine this certain range to be an average of the ranges of the firstset, among other possibilities. Additionally or alternatively, thecomputing system could assemble a point cloud based on the first set ofranges and could use this point cloud as basis for identifying thenearby object in accordance with object recognition technique(s).

However, if the computing system determines that the second set ofranges should be used as a basis for object detection, the computingsystem may responsively use the second set of ranges rather than thefirst set of ranges as basis for object detection. For instance, thecomputing system may determine based on the second set of ranges that anearby object is positioned at a certain range away from the LIDARdevice. The computing system could determine this certain range to beone of the ranges of the second set or could determine this certainrange to be an average of the ranges of the second set, among otherpossibilities. Additionally or alternatively, the computing system couldassemble a point cloud based on the second set of ranges and could usethis point cloud as basis for identifying the nearby object inaccordance with object recognition technique(s). Other instances arealso possible.

In some implementations, assuming that the alternate range hypothesisgenerated for the second return light pulses could be referred to as asecond alternate range hypothesis, the computing system couldadditionally generate a first alternate range hypothesis for the firstreturn light pulses and could use this first alternate range hypothesisto help overcome range ambiguity. Namely, the computing system could usethis first alternate range hypothesis as further basis to determinewhether to use the first or second set of ranges for purposes of objectdetection.

In particular, the computing system could make a comparison between thefirst alternate range hypothesis and the second alternate rangehypothesis, and could then determine whether to use the first or secondset of ranges for purposes of object detection based on the comparison.

In one example, the comparison could be a determination of whether afirst far range hypothesis more closely resembles known object(s) than asecond far range hypothesis, or vice versa. For instance, if thecomputing system determines that the first far range hypothesis isrepresentative of one or more known objects and that the second farrange hypothesis is not representative of any known object, then thecomputing system may responsively determine the first far rangehypothesis more closely resembles known object(s) than the second farrange hypothesis. Whereas, if the computing system determines that thesecond far range hypothesis is representative of one or more knownobjects and that the first far range hypothesis is not representative ofany known object, then the computing system may responsively determinethe second far range hypothesis more closely resembles known object(s)than the first far range hypothesis.

However, if the computing system determines that both the first andsecond far range hypotheses are respectively representative of knownobject(s), then the computing system could use object recognitiontechnique(s) to determine which of these far range hypotheses moreclosely resembles known object(s). For instance, the computing systemmay determine that the first range hypothesis matches a known objectwith a first level of certainty (e.g., a 25% match) and that the secondrange hypothesis matches a known object with a second level of certainty(e.g., a 95% match). Based on a determination that the second level ofcertainty is higher than the first level of certainty, the computingsystem could responsively determine that the second far range hypothesismore closely resembles a known object compared with the first far rangehypothesis. Other instances are possible as well.

In this example, if the computing system determines that the first farrange hypothesis more closely resembles known object(s) than the secondfar range hypothesis, then the computing system may determine that thefirst far range hypothesis is more likely to be correct than the secondrange hypothesis. Namely, that the second return light pulses morelikely each respectively correspond a most recent detection period andthat the first return light pulses more likely each respectivelycorrespond to a preceding detection period. Therefore, in response todetermining that the first far range hypothesis more closely resembleknown object(s) than the second far range hypothesis, the computingsystem may determine that the computing system should use, for purposesof object detection, the second set of ranges associated with the secondreturn light pulses rather than the first set of ranges associated withthe first return light pulses.

In contrast, if the computing system determines that the second farrange hypothesis more closely resembles known object(s) than the firstfar range hypothesis, then the computing system may determine that thesecond far range hypothesis is more likely to be correct than the firstrange hypothesis. Namely, that the first return light pulses more likelyeach respectively correspond a most recent detection period and that thesecond return light pulses more likely each respectively correspond to apreceding detection period. Therefore, in response to determining thatthe second far range hypothesis more closely resemble known object(s)than the first far range hypothesis, the computing system may determinethat the computing system should use, for purposes of object detection,the first set of ranges associated with the first return light pulsesrather than the second set of ranges associated with the second returnlight pulses.

In another example, the comparison could be a comparison of how similarranges of a first far range hypothesis are to one another relative tohow similar ranges of a second far range hypothesis are to one another.For instance, the computing system could determine that ranges of thesecond far range hypothesis match one another and that ranges of thefirst far range hypothesis are different from one another. As a result,the computing system may responsively determine that ranges of thesecond far range hypothesis are more similar to one another compared tosimilarity of ranges in the first far range hypothesis. Other instancesare possible as well.

In this example, if the computing system makes a determination thatranges of the first far range hypothesis are more similar to one anothercompared to similarity of ranges in the second far range hypothesis,then the computing system may determine that the first far rangehypothesis is more likely to be correct than the second far rangehypothesis. Namely, that the second return light pulses more likely eachrespectively correspond a most recent detection period and that thefirst return light pulses more likely each respectively correspond to apreceding detection period. Therefore, in response to making thisdetermination, the computing system may determine that the computingsystem should use, for purposes of object detection, the second set ofranges associated with the second return light pulses rather than thefirst set of ranges associated with the first return light pulses.

In contrast, if the computing system makes a determination that rangesof the second far range hypothesis are more similar to one anothercompared to similarity of ranges in the first far range hypothesis, thenthe computing system may determine that the second far range hypothesisis more likely to be correct than the first range hypothesis. Namely,that the first return light pulses more likely each respectivelycorrespond a most recent detection period and that the second returnlight pulses more likely each respectively correspond to a precedingdetection period. Therefore, in response to making this determination,the computing system may determine that the computing system should use,for purposes of object detection, the first set of ranges associatedwith the first return light pulses rather than the second set of rangesassociated with the second return light pulses. Other examples are alsopossible.

In this manner, one or more alternate range hypotheses could helpovercome range ambiguity and thus help detect nearby object(s) with ahigher level of certainty. Such enhanced detection of nearby object(s)could be used by the computing system to optimize navigation decisionsfor a vehicle that operates in an autonomous mode, among other outcomes.

FIGS. 13A-13B and 14A-14B next illustrate how one or more alternaterange hypotheses could help overcome range ambiguity and thus helpdetect nearby object(s) with a higher level of certainty.

In particular, FIG. 13A shows the emission time sequence #4 introducedabove. Here again, the computing system respectively determines rangescorresponding to light pulses B, D, and F according to a time delayrelative to an emission time of a previously emitted light pulse.Namely, as shown in FIG. 13A, the computing system determines thatreturn light pulses B has a detection time of 533 ns relative toemission time B, that return light pulses D has a detection time of 533ns relative to emission time D, and that return light pulses F has adetection time of 533 ns relative to emission time F. As shown in FIG.13B, these detection times of return light pulses B, D, F each have acorresponding range of 80 m. Therefore, these corresponding rangesresult in a set of ranges 1300 considered to be a far range hypothesisof a distant object being positioned at 80 m away from the LIDAR device.

In this example, the computing system could determine that the far rangehypothesis is likely correct based on the ranges 1300 beingsubstantially similar to one another. Based on a determination that thefar range hypothesis is likely correct, the computing system may in turndetermine that a close range hypothesis associated with return lightpulses B, D, and F (e.g., above-mentioned ranges 904) is likelyincorrect. Consequently, based on a determination that the far rangehypothesis is likely correct, the computing system may responsivelydetermine with a higher level of certainty that a close range hypothesisassociated with light pulses A, C, E, and G (e.g., above-mentionedranges 902) should be used for object detection, thereby resolving therange ambiguity that may arise due to detection of multiple return lightpulses respectively in one or more detection periods.

Furthermore, FIGS. 14A-14B illustrate how an additional alternate rangehypothesis could help overcome range ambiguity with an even higher levelof certainty. In particular, FIG. 14A also shows the emission timesequence #4. But in this case, the computing system respectivelydetermines ranges corresponding light pulses C, E, and G according to atime delay relative to an emission time of a previously emitted lightpulse. Namely, as shown in FIG. 14C, the computing system determinesthat return light pulses C has a detection time of 675 ns relative toemission time B, that return light pulses E has a detection time of 725ns relative to emission time D, and that return light pulses G has adetection time of 750 ns relative to emission time F. And as shown inFIG. 14B, these detection times of return light pulses C, E, and Grespectively have corresponding range of 101.35 m, 108.8 m, and 112.6 m.Therefore, these corresponding ranges result in a set of ranges 1400considered to be another far range hypothesis.

In this example, the computing system could determine that ranges 1300are more similar to one another compared to similarity of ranges 1400(e.g., that ranges 1400 are scattered relative to ranges 1300).Consequently, the computing system could responsively determine with ahigher level of certainty that a close range hypothesis associated withlight pulses A, C, E, and G (e.g., above-mentioned ranges 902) should beused for object detection, thereby resolving the range ambiguity thatmay arise due to detection of multiple return light pulses respectivelyin one or more detection periods. Other illustrations are possible awell.

d. Operating an Autonomous Vehicle Based on a Selected Distance

FIG. 15 is a flowchart illustrating a method 1500, according to anexample implementation. In particular, method 1500 may be implemented toselect a distance corresponding to a received signal associated with areflected return light pulse, and to then operate an autonomous vehiclebased on the selection. Please note that any of the implementationsdiscussed herein could be applied in the context of method 1500.

At block 1502, method 1500 involves receiving a signal associated with areflection, by an object, of a light pulse emitted by a LIDAR device ofthe autonomous vehicle.

At block 1504, method 1500 involves calculating a first distance to theobject based on a first time, the first time corresponding to a priorlight pulse emitted by the LIDAR device of the autonomous vehicle.

At block 1506, method 1500 involves calculating a second distance to theobject based on a second time, the second time corresponding to adifferent prior light pulse emitted by the LIDAR device of theautonomous vehicle.

At block 1508, method 1500 involves operating the autonomous vehiclebased on a selection between the first distance and second distance. Forexample, the selection between the first distance and second distancecould be based on a plurality of received signals associated withrespective reflections, by the object, of a plurality of light pulsesemitted by the LIDAR device. Generally, one or more of the plurality oflight pulses could be emitted according to a timing that deviates from aperiodicity by a pseudo-random duration.

VII. CONTROLLING A VEHICLE BASED ON SCANS BY THE LIDAR DEVICE

As noted, a computing system may operate a vehicle based on scansreceived from the LIDAR device disclosed herein. In particular, thecomputing system may receive from the LIDAR device scans of anenvironment around the vehicle. And the computing system may operate thevehicle based at least on the scans of the environment received from theLIDAR device.

More specifically, the computing system may operate the LIDAR device 100to emit light into the environment. Also, the computing system mayreceive from the LIDAR device 100 data representative of detections ofreflected light. And by comparing detected light beams with emittedlight beams, the computing system may determine at least one aspect ofone or more objects in the environment.

For example, by comparing a time when a plurality of light beams wereemitted by the transmitter of the LIDAR device 100 and a time when thereceiver of the LIDAR device 100 detected reflected light, a distancebetween the LIDAR device 100 and an object in the environment may bedetermined. In other examples, aspects such as shape, color, material,etc. may also be determined based on various comparisons between emittedlight and detected light.

With this arrangement, the computing system could determine athree-dimensional (3D) representation of the environment based on datafrom the LIDAR device 100. For example, the 3D representation may begenerated by the computing system as a 3D point cloud based on the datafrom the LIDAR device 100. Each point of the 3D cloud, for example, maybe associated with a reflected light pulse. As such, the computingsystem may (e.g., continuously or from time-to-time) generate 3Drepresentations of the environment or portions thereof. And thecomputing system could then control operation of the vehicle based onevaluation of such 3D representations of the environment.

By way of example, the vehicle may be operated in an autonomous mode. Inthis example, the computing system may utilize 3D representations tonavigate the vehicle (e.g., adjust speed, direction, etc.) safely byavoiding obstacles among other possibilities. The obstacles or objects,for example, may be detected and/or identified using an image processingalgorithm or other computing method to analyze the 3D representationsand detect and/or identify the various obstacles or objects. As anotherexample, the vehicle may be operated in a partially autonomous or manualmode. In this example, the vehicle may notify a driver or operator ofthe vehicle of the presence or distance to various objects or changingroad conditions (e.g., street lights, street signs, etc.), such as bycausing a display or a speaker in the vehicle to present informationregarding one or more objects in the environment. Other examples arepossible as well.

FIG. 16 next illustrates example operation of the vehicle 300 based onscans of an environment 1600 received from the LIDAR device 200. Inaccordance with the present disclosure, the vehicle's computing systemmay use data received from the LIDAR device 200 to detect and identifydistant object(s), such as a road sign 404 for example. In this regard,the computing system may determine based on the data that the road sign404 is representative of an exit that the vehicle 300 should ideallytake in order to arrive at a desired destination. In response to makingthat determination, the computing system may then operate the vehicle300 to switch from driving on lane 1 to driving on lane 2.

In practice, the computing system may distinguish between these lanes byrecognizing lane markers within 3D representations of the environment1600. For instance, the vehicle's computing system may use data receivedfrom the LIDAR device 200 to detect and identify the nearby lane markerthat separates lane 1 from lane 2. Moreover, before operating thevehicle to switch lanes, the computing system may scan the environmentto detect and identify objects, so that computing system can operate thevehicle 300 in a way that avoids those detected/identified objects whilealso operating the vehicle 300 to switch lanes.

For instance, the computing system may use data received from the LIDARdevice 200 to detect and identify the nearby vehicle 1602 as well as todetect and identify road sign 402. Based on thosedetections/identifications, the computing system may operate the vehicle300 in a way that avoids the vehicle 1602 and road sign 402 while alsooperating the vehicle 300 to switch from driving on lane 1 to driving onlane 2. Other illustrations are possible as well.

VIII. EXAMPLE ARRANGEMENT OF A VEHICLE

Finally, FIG. 17 is a simplified block diagram of a vehicle 1700,according to an example embodiment. The vehicle 1700 may be similar tothe vehicle 300, and may include a LIDAR device similar to the LIDARdevice 100. Further, the vehicle 1700 may be configured to performfunctions and methods herein such as method 800 and/or method 1000. Asshown, the vehicle 1700 includes a propulsion system 1702, a sensorsystem 1704, a control system 1706 (could also be referred to as acontroller 1706), peripherals 1708, and a computer system 1710. Vehicle1700 may be, for example, a motor vehicle, railed vehicle, watercraft,or aircraft. In other embodiments, the vehicle 1700 may include more,fewer, or different systems, and each system may include more, fewer, ordifferent components.

Additionally, the systems and components shown may be combined ordivided in any number of ways. For instance, the control system 1706 andthe computer system 1710 may be combined into a single system thatoperates the vehicle 1700 in accordance with various operations.

The propulsion system 1702 may be configured to provide powered motionfor the vehicle 1700. As shown, the propulsion system 1702 includes anengine/motor 1718, an energy source 1720, a transmission 1722, andwheels/tires 1724.

The engine/motor 1718 may be or include any combination of an internalcombustion engine, an electric motor, a steam engine, and a Sterlingengine. Other motors and engines are possible as well. In someembodiments, the propulsion system 1702 may include multiple types ofengines and/or motors. For instance, a gas-electric hybrid car mayinclude a gasoline engine and an electric motor. Other examples arepossible.

The energy source 1720 may be a source of energy that powers theengine/motor 1718 in full or in part. That is, the engine/motor 918 maybe configured to convert the energy source 1720 into mechanical energy.Examples of energy sources 1720 include gasoline, diesel, propane, othercompressed gas-based fuels, ethanol, solar panels, batteries, and othersources of electrical power. The energy source(s) 1720 may additionallyor alternatively include any combination of fuel tanks, batteries,capacitors, and/or flywheels. In some embodiments, the energy source1720 may provide energy for other systems of the vehicle 1700 as well.

The transmission 1722 may be configured to transmit mechanical powerfrom the engine/motor 1718 to the wheels/tires 1724. To this end, thetransmission 1722 may include a gearbox, clutch, differential, driveshafts, and/or other elements. In embodiments where the transmission1722 includes drive shafts, the drive shafts may include one or moreaxles that are configured to be coupled to the wheels/tires 1724.

The wheels/tires 1724 of vehicle 1700 may be configured in variousformats, including a bicycle/motorcycle, tricycle, car/truck four-wheelformat, or a rail. Other wheel/tire formats are possible as well, suchas those including six or more wheels. In any case, the wheels/tires1724 may be configured to rotate differentially with respect to otherwheels/tires 1724. In some embodiments, the wheels/tires 1724 mayinclude at least one wheel that is fixedly attached to the transmission1722 and at least one tire coupled to a rim of the wheel that could makecontact with the driving surface. The wheels/tires 1724 may include anycombination of metal and rubber, or combination of other materials. Thepropulsion system 1702 may additionally or alternatively includecomponents other than those shown.

The sensor system 1704 may include a number of sensors configured tosense information about an environment in which the vehicle 1700 islocated, as well as one or more actuators 1736 configured to modify aposition and/or orientation of the sensors. As shown, the sensors of thesensor system 1704 include a Global Positioning System (GPS) 1726, aninertial measurement unit (IMU) 1728, a RADAR unit 1730, a laserrangefinder and/or LIDAR unit 1732, and a camera 1734. The sensor system1704 may include additional sensors as well, including, for example,sensors that monitor internal systems of the vehicle 1700 (e.g., an O₂monitor, a fuel gauge, an engine oil temperature, etc.). Other sensorsare possible as well.

The GPS 1726 may be any sensor (e.g., location sensor) configured toestimate a geographic location of the vehicle 1700. To this end, the GPS1726 may include a transceiver configured to estimate a position of thevehicle 1700 with respect to the Earth. The GPS 1726 may take otherforms as well.

The IMU 1728 may be any combination of sensors configured to senseposition and orientation changes of the vehicle 1700 based on inertialacceleration. In some embodiments, the combination of sensors mayinclude, for example, accelerometers and gyroscopes. Other combinationsof sensors are possible as well.

The RADAR unit 1730 may be any sensor configured to sense objects in theenvironment in which the vehicle 1700 is located using radio signals. Insome embodiments, in addition to sensing the objects, the RADAR unit1730 may additionally be configured to sense the speed and/or heading ofthe objects.

Similarly, the laser range finder or LIDAR unit 1732 may be any sensorconfigured to sense objects in the environment in which the vehicle 1700is located using lasers. For example, LIDAR unit 1732 may include one ormore LIDAR devices, at least some of which may take the form the LIDARdevice 100 disclosed herein.

The camera 1734 may be any camera (e.g., a still camera, a video camera,etc.) configured to capture images of the environment in which thevehicle 1700 is located. To this end, the camera may take any of theforms described above. The sensor system 1704 may additionally oralternatively include components other than those shown.

The control system 1706 may be configured to control operation of thevehicle 1700 and its components. To this end, the control system 1706may include a steering unit 1738, a throttle 1740, a brake unit 1742, asensor fusion algorithm 1744, a computer vision system 1746, anavigation or pathing system 1748, and an obstacle avoidance system1750.

The steering unit 1738 may be any combination of mechanisms configuredto adjust the heading of vehicle 1700. The throttle 1740 may be anycombination of mechanisms configured to control the operating speed ofthe engine/motor 1718 and, in turn, the speed of the vehicle 1700. Thebrake unit 1742 may be any combination of mechanisms configured todecelerate the vehicle 1700. For example, the brake unit 1742 may usefriction to slow the wheels/tires 1724. As another example, the brakeunit 1742 may convert the kinetic energy of the wheels/tires 1724 toelectric current. The brake unit 1742 may take other forms as well.

The sensor fusion algorithm 1744 may be an algorithm (or a computerprogram product storing an algorithm) configured to accept data from thesensor system 1704 as an input. The data may include, for example, datarepresenting information sensed at the sensors of the sensor system1704. The sensor fusion algorithm 1744 may include, for example, aKalman filter, a Bayesian network, an algorithm for some of thefunctions of the methods herein, or any other algorithm. The sensorfusion algorithm 1744 may further be configured to provide variousassessments based on the data from the sensor system 1704, including,for example, evaluations of individual objects and/or features in theenvironment in which the vehicle 1700 is located, evaluations ofparticular situations, and/or evaluations of possible impacts based onparticular situations. Other assessments are possible as well.

The computer vision system 1746 may be any system configured to processand analyze images captured by the camera 1734 in order to identifyobjects and/or features in the environment in which the vehicle 1700 islocated, including, for example, traffic signals and obstacles. To thisend, the computer vision system 1746 may use an object recognitionalgorithm, a Structure from Motion (SFM) algorithm, video tracking, orother computer vision techniques. In some embodiments, the computervision system 1746 may additionally be configured to map theenvironment, track objects, estimate the speed of objects, etc.

The navigation and pathing system 1748 may be any system configured todetermine a driving path for the vehicle 1700. The navigation andpathing system 1748 may additionally be configured to update the drivingpath dynamically while the vehicle 1700 is in operation. In someembodiments, the navigation and pathing system 1748 may be configured toincorporate data from the sensor fusion algorithm 1744, the GPS 1726,the LIDAR unit 1732, and one or more predetermined maps so as todetermine the driving path for vehicle 1700.

The obstacle avoidance system 1750 may be any system configured toidentify, evaluate, and avoid or otherwise negotiate obstacles in theenvironment in which the vehicle 1700 is located. The control system1706 may additionally or alternatively include components other thanthose shown.

Peripherals 1708 may be configured to allow the vehicle 1700 to interactwith external sensors, other vehicles, external computing devices,and/or a user. To this end, the peripherals 1708 may include, forexample, a wireless communication system 1752, a touchscreen 1754, amicrophone 1756, and/or a speaker 1758.

The wireless communication system 1752 may be any system configured towirelessly couple to one or more other vehicles, sensors, or otherentities, either directly or via a communication network. To this end,the wireless communication system 1752 may include an antenna and achipset for communicating with the other vehicles, sensors, servers, orother entities either directly or via a communication network. Thechipset or wireless communication system 1752 in general may be arrangedto communicate according to one or more types of wireless communication(e.g., protocols) such as Bluetooth, communication protocols describedin IEEE 802.11 (including any IEEE 802.11 revisions), cellulartechnology (such as GSM, CDMA, UMTS, EV-DO, WiMAX, or LTE), Zigbee,dedicated short range communications (DSRC), and radio frequencyidentification (RFID) communications, among other possibilities. Thewireless communication system 1752 may take other forms as well.

The touchscreen 1754 may be used by a user to input commands to thevehicle 1700. To this end, the touchscreen 1754 may be configured tosense at least one of a position and a movement of a user's finger viacapacitive sensing, resistance sensing, or a surface acoustic waveprocess, among other possibilities. The touchscreen 1754 may be capableof sensing finger movement in a direction parallel or planar to thetouchscreen surface, in a direction normal to the touchscreen surface,or both, and may also be capable of sensing a level of pressure appliedto the touchscreen surface. The touchscreen 1754 may be formed of one ormore translucent or transparent insulating layers and one or moretranslucent or transparent conducting layers. The touchscreen 1754 maytake other forms as well.

The microphone 1756 may be configured to receive audio (e.g., a voicecommand or other audio input) from a user of the vehicle 1700.Similarly, the speakers 1758 may be configured to output audio to theuser of the vehicle 1700. The peripherals 1708 may additionally oralternatively include components other than those shown.

The computer system 1710 may be configured to transmit data to, receivedata from, interact with, and/or control one or more of the propulsionsystem 1702, the sensor system 1704, the control system 1706, and theperipherals 1708. To this end, the computer system 1710 may becommunicatively linked to one or more of the propulsion system 1702, thesensor system 1704, the control system 1706, and the peripherals 1708 bya system bus, network, and/or other connection mechanism (not shown).

In one example, the computer system 1710 may be configured to controloperation of the transmission 1722 to improve fuel efficiency. Asanother example, the computer system 1710 may be configured to cause thecamera 1734 to capture images of the environment. As yet anotherexample, the computer system 1710 may be configured to store and executeinstructions corresponding to the sensor fusion algorithm 1744. As stillanother example, the computer system 1710 may be configured to store andexecute instructions for determining a 3D representation of theenvironment around the vehicle 1700 using the LIDAR unit 1732. Otherexamples are possible as well. Thus, the computer system 1710 couldfunction as the controller for the LIDAR unit 1732.

As shown, the computer system 1710 includes the processor 1712 and datastorage 1714. The processor 1712 may include one or more general-purposeprocessors and/or one or more special-purpose processors. To the extentthe processor 1712 includes more than one processor, such processorscould work separately or in combination. Data storage 1714, in turn, mayinclude one or more volatile and/or one or more non-volatile storagecomponents, such as optical, magnetic, and/or organic storage, and datastorage 1714 may be integrated in whole or in part with the processor1712.

In some embodiments, data storage 1714 may contain instructions 1716(e.g., program logic) executable by the processor 1712 to executevarious vehicle functions (e.g., method 500, etc.). Data storage 1714may contain additional instructions as well, including instructions totransmit data to, receive data from, interact with, and/or control oneor more of the propulsion system 1702, the sensor system 1704, thecontrol system 1706, and/or the peripherals 1708. The computer system1710 may additionally or alternatively include components other thanthose shown.

As shown, the vehicle 1700 further includes a power supply 1760, whichmay be configured to provide power to some or all of the components ofthe vehicle 1700. To this end, the power supply 1760 may include, forexample, a rechargeable lithium-ion or lead-acid battery. In someembodiments, one or more banks of batteries could be configured toprovide electrical power. Other power supply materials andconfigurations are possible as well. In some embodiments, the powersupply 1760 and energy source 1720 may be implemented together as onecomponent, as in some all-electric cars.

In some embodiments, the vehicle 1700 may include one or more elementsin addition to or instead of those shown. For example, the vehicle 1700may include one or more additional interfaces and/or power supplies.Other additional components are possible as well. In such embodiments,data storage 1714 may further include instructions executable by theprocessor 1712 to control and/or communicate with the additionalcomponents.

Still further, while each of the components and systems are shown to beintegrated in the vehicle 1700, in some embodiments, one or morecomponents or systems may be removably mounted on or otherwise connected(mechanically or electrically) to the vehicle 1700 using wired orwireless connections. The vehicle 1700 may take other forms as well.

IX. CONCLUSION

The particular arrangements shown in the Figures should not be viewed aslimiting. It should be understood that other implementations may includemore or less of each element shown in a given Figure. Further, some ofthe illustrated elements may be combined or omitted. Yet further, anexemplary implementation may include elements that are not illustratedin the Figures.

Additionally, while various aspects and implementations have beendisclosed herein, other aspects and implementations will be apparent tothose skilled in the art. The various aspects and implementationsdisclosed herein are for purposes of illustration and are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims. Other implementations may be utilized, and otherchanges may be made, without departing from the spirit or scope of thesubject matter presented herein. It will be readily understood that theaspects of the present disclosure, as generally described herein, andillustrated in the figures, can be arranged, substituted, combined,separated, and designed in a wide variety of different configurations,all of which are contemplated herein.

I claim:
 1. A method comprising: operating, by a computing system, aLight Detection and Ranging (LIDAR) device to emit light pulses atemission times in accordance with an emission time sequence, wherein theemission time sequence includes a time-varying dither, and to detectreturn light pulses in accordance with a detection time sequence,wherein the detection time sequence includes, for each emitted lightpulse, a corresponding detection period for detection of a correspondingreturn light pulse, and wherein a detection time of a return light pulserelative to a corresponding emission time of a corresponding emittedlight pulse is indicative of a range to an object that reflected thecorresponding emitted light pulse; making a determination, by thecomputing system, that the LIDAR device detected return light pulsesduring corresponding detection periods for each of two or more emittedlight pulses; in response to making the determination, determining, bythe computing system, that (i) the detected return light pulses havedetection times relative to corresponding emission times of a pluralityof first emitted light pulses that are indicative of a first set ofranges and (ii) the detected return light pulses have detection timesrelative to corresponding emission times of a plurality of secondemitted light pulses that are indicative of a second set of ranges;selecting, by the computing system, between using the first set ofranges as a basis for object detection and using the second set ofranges as a basis for object detection; and engaging, by the computingsystem, in object detection in accordance with the selecting.
 2. Themethod of claim 1, wherein making a determination that the LIDAR devicedetected return light pulses during corresponding detection periods foreach of two or more emitted light pulses comprises making adetermination that the LIDAR device detected return light pulses duringcorresponding detection periods for each of the plurality of firstemitted light pulses.
 3. The method of claim 2, wherein the LIDAR devicehas a nominal unambiguous detection range, wherein ranges of the firstset are within the nominal unambiguous detection range of the LIDARdevice, and wherein ranges of the second set are outside the nominalunambiguous detection range of the LIDAR device.
 4. The method of claim2, wherein ranges of the second set are greater than ranges of the firstset.
 5. The method of claim 1, further comprising: determining, by thecomputing system, that the second set of ranges is representative of atleast one known object, wherein the selecting comprises, in response todetermining that the second set of ranges is representative of at leastone known object, selecting use of the second set of ranges as a basisfor object detection.
 6. The method of claim 1, further comprising:determining, by the computing system, that the second set of ranges isnot representative of at least one known object, wherein the selectingcomprises, in response to determining that the second set of ranges isnot representative of at least one known object, selecting use of thefirst set of ranges as a basis for object detection.
 7. The method ofclaim 1, further comprising: determining, by the computing system, thatranges of the second set are substantially similar to one another,wherein the selecting comprises, in response to determining that rangesof the second set are substantially similar to one another, selectinguse of the second set of ranges as a basis for object detection.
 8. Themethod of claim 1, further comprising: determining, by the computingsystem, that ranges of the second set are not substantially similar toone another, wherein the selecting comprises, in response to determiningthat ranges of the second set are not substantially similar to oneanother, selecting use of the first set of ranges as a basis for objectdetection.
 9. The method of claim 1, wherein the LIDAR device ispositioned on a vehicle, and wherein engaging in object detection inaccordance with the selecting comprises, in accordance with theselecting, engaging in detection of objects positioned in an environmentaround the vehicle.
 10. The method of claim 1, wherein the LIDAR deviceis positioned on a vehicle, and wherein the computing system isconfigured to operate the vehicle based at least on scans by the LIDARdevice of an environment around the vehicle.
 11. A computing systemcomprising: one or more processors; a non-transitory computer readablemedium; and program instructions stored on the non-transitory computerreadable medium and executable by the one or more processors to: operatea Light Detection and Ranging (LIDAR) device to emit light pulses atemission times in accordance with an emission time sequence, wherein theemission time sequence includes a time-varying dither, and to detectreturn light pulses in accordance with a detection time sequence,wherein the detection time sequence includes, for each emitted lightpulse, a corresponding detection period for detection of a correspondingreturn light pulse, and wherein a detection time of a return light pulserelative to a corresponding emission time of a corresponding emittedlight pulse is indicative of a range to an object that reflected thecorresponding emitted light pulse; make a determination that the LIDARdevice detected return light pulses during corresponding detectionperiods for each of two or more emitted light pulses; in response tomaking the determination, determine that (i) the detected return lightpulses have detection times relative to corresponding emission times ofa plurality of first emitted light pulses that are indicative of a firstset of ranges and (ii) the detected return light pulses have detectiontimes relative to corresponding emission times of a plurality of secondemitted light pulses that are indicative of a second set of ranges;select between using the first set of ranges as a basis for objectdetection and using the second set of ranges as a basis for objectdetection; and engage in object detection in accordance with theselecting.
 12. The computing system of claim 11, wherein the programinstruction are further executable to: determine that the second set ofranges is representative of at least one known object, wherein theselecting comprises, in response to determining that the second set ofranges is representative of at least one known object, selecting use ofthe second set of ranges as a basis for object detection.
 13. Thecomputing system of claim 11, wherein the program instruction arefurther executable to: determine that ranges of the second set aresubstantially similar to one another, wherein the selecting comprises,in response to determining that ranges of the second set aresubstantially similar to one another, selecting use of the second set ofranges as a basis for object detection.
 14. The computing system ofclaim 11, wherein the LIDAR device is positioned on a vehicle, whereinengaging in object detection in accordance with the furtherdetermination comprises, in accordance with the selecting, engaging indetection of objects positioned in an environment around the vehicle,and wherein the program instruction are further executable to operatethe vehicle based at least on the detection of objects positioned in theenvironment around the vehicle.
 15. A method comprising: operating, by acomputing system, a Light Detection and Ranging (LIDAR) device to emitlight pulses at emission times in accordance with an emission timesequence, wherein the emission time sequence includes a time-varyingdither, and to detect return light pulses in accordance with a detectiontime sequence, wherein the detection time sequence includes, for eachemitted light pulse, a corresponding detection period for detection of acorresponding return light pulse, and wherein a detection time of areturn light pulse relative to a corresponding emission time of acorresponding emitted light pulse is indicative of a range to an objectthat reflected the corresponding emitted light pulse; determining, bythe computing system, that the LIDAR device detected a set of multiplereturn light pulses during corresponding detection periods for each of aplurality of first emitted light pulses, wherein each set of multiplereturn light pulses includes at least a respective first return lightpulse and a respective second return light pulse; making adetermination, by the computing system, that the first return lightpulses correspond to the plurality of first emitted light pulses andthat the second return light pulses potentially correspond to aplurality of second emitted light pulses; in response to making thedetermination, determining, by the computing system, that the secondreturn light pulses have detection times relative to correspondingemission times of the plurality of second emitted light pulses that areindicative of a particular set of ranges; making a furtherdetermination, by the computing system, of whether or not to use theparticular set of ranges as a basis for object detection; and engaging,by the computing system, in object detection in accordance with thefurther determination.
 16. The method of claim 15, wherein making thefurther determination comprises: determining whether or not theparticular set of ranges is representative of at least one known object;if the computing system determines that the particular set of ranges isrepresentative of at least one known object, then responsivelydetermining that the particular set of ranges is to be used as a basisfor object detection; and if the computing system determines that theparticular set is not representative of at least one known object, thenresponsively determining that the particular set of ranges is not to beused as a basis for object detection.
 17. A method comprising:operating, by a computing system, a Light Detection and Ranging (LIDAR)device to emit light pulses at emission times in accordance with anemission time sequence, wherein the emission time sequence includes atime-varying dither, and to detect return light pulses in accordancewith a detection time sequence, wherein the detection time sequenceincludes, for each emitted light pulse, a corresponding detection periodfor detection of a corresponding return light pulse, and wherein adetection time of a return light pulse relative to a correspondingemission time of a corresponding emitted light pulse is indicative of arange to an object that reflected the corresponding emitted light pulse;determining, by the computing system, that the LIDAR device detected aset of multiple return light pulses during corresponding detectionperiods for each of a plurality of first emitted light pulses, whereineach set of multiple return light pulses includes at least a respectivefirst return light pulse and a respective second return light pulse;determining, by the computing system, that (i) the first return lightpulses have detection times relative to corresponding emission times ofthe plurality of first emitted light pulses that are indicative of afirst set of ranges, (ii) the second return light pulses have detectiontimes relative to corresponding emission times of the plurality of firstemitted light pulses that are indicative of a second set of ranges, and(iii) the second return light pulses have detection times relative tocorresponding emission times of a plurality of second emitted lightpulses that are indicative of a third set of ranges; based on the thirdset of ranges, selecting, by the computing system, between using thefirst set of ranges as a basis for object detection and using the secondset of ranges as a basis for object detection; and engaging, by thecomputing system, in object detection in accordance with the selecting.18. The method of claim 17, wherein selecting based on the third set ofranges comprises: making a determination of whether or not the third setof ranges is representative of at least one known object; if thedetermination is that the third set of ranges is representative of atleast one known object, then, responsive to making the determination,selecting use of the first set of ranges as a basis for objectdetection; and if the determination is that the third set of ranges isnot representative of at least one known object, then, responsive tomaking the determination, selecting use of the second set of ranges as abasis for object detection.
 19. A method for operating an autonomousvehicle, comprising: receiving a signal associated with a reflection, byan object, of a light pulse emitted by a LIDAR device of the autonomousvehicle, wherein the reflection is detected by the LIDAR device at adetection time; calculating a first distance to the object based on thedetection time and a first time, the first time corresponding to a priorlight pulse emitted by the LIDAR device of the autonomous vehicle;calculating a second distance to the object based on the detection timeand a second time, the second time corresponding to a different priorlight pulse emitted by the LIDAR device of the autonomous vehicle; andoperating the autonomous vehicle based on a selection between the firstdistance and second distance.
 20. The method of claim 19, wherein theselection between the first distance and second distance is based on aplurality of received signals associated with respective reflections, bythe object, of a plurality of light pulses emitted by the LIDAR deviceand wherein one or more of the plurality of light pulses are emittedaccording to a timing that deviates from a periodicity by apseudo-random duration.